MULTIPLE FACILITY OPERATING SYSTEM ARCHITECTURE

Abstract: A computer system employing a multiple facility operating system architecture is disclosed. The computer system includes a plurality of processor units (12, 14, 16) for implementing a predetermined set of peer-level facilities (162, 164, 166, 168) wherein each peer-level facility includes a plurality of related functions and a communications bus (22) interconnecting the processor units. Each of the processor units includes a central processor (30, 80, 100) and the stored program (68, 86, 134) that, upon execution, provides for the implementation of a predetermined peer-level facility and for performing a multi-tasking interface function. The multi-tasking interface function is responsive to control messages for selecting for execution functions of the predetermined peer-level facility and is responsive to the predetermined peer-level facility for providing control messages to request or to respond to the performance of functions of another peer-level facility of the computer system. The multi-tasking interface functions of the processor units communicate among one another via the communication bus.

Description: MULTIPLE FACILITY OPERATING SYSTEM ARCHITECTURE CROSS-REFERENCE TO RELATED APPLICATIONS The present application is related to the following U.S. Patent Applications: 1. PARALLEL I/O NETWORK FILE SERVER ARCHITECTURE, inventors: John Row, Larry Boucher, William Pitts, and Steve Blightman; 2. ENHANCED VMEBUS PROTOCOL UTILIZING SYNCHRONOUS HANDSHAKING AND BLOCK MODE DATA TRANSFER, inventor: Daryl D. Starr; 2. BUS LOCKING FIFO MULTI-PROCESSOR COMMUNICATIONS SYSTEM UTILIZING PSEUDOSYNCHRONOUS HANDSHAKING AND BLOCK MODE DATA TRANSFER invented by William Pitts, Stephen Blightman and Daryl D. Starr; 3. IMPROVED FAST TRANSFER DIRECT MEMORY ACCESS CONTROLLER, invented by Daryl Starr, Stephen Blightman and Larry Boucher. The above applications are all assigned to the assignee of the present invention and are all expressly incorporated herein by reference. Field of the Invention: The present invention is generally related to operating system software architectures and, in particular, to a multi-processor operating system architecture based on multiple independent multi¬ tasking process kernels. Background of the Invention: The desire to improve productivity, in circumstances involving computers, is often realized by an improvement in computing throughput. Conventional file servers are recognized as being a limiting factor in the potential productivity associated with their client workstations. A file server is typically a conventional computer system coupled through a communications network, such as Ethernet, to client workstations and potentially other workstation file servers. The file server operates to provide a common resource base to its clients. The primary resource is typically the central storage and management of data files, but additional services including single point execution of certain types of programs, electronic mail delivery and gateway connection to other file servers and services are generally also provided. The client workstations may utilize any of a number of communication network protocols to interact with the file server. Perhaps the most commonly known, if not most widely used, protocol suite is TCP/IP. This protocol suite and its supporting utility programs, provide for the creation of logical communication channels between multiple client workstations and a file server. These communication channels are generally optimized for point-to-point file transfers, i.e., multi-user file access control or activity administration is not provided. In addition, the supporting utility programs for these protocols impose a significant degree of user interaction in order to initiate file transfers as well as the entire responsibility to manage the files once transferred. Recently, a number of network connected remote file system mechanisms has been developed to provide clients with a single consistent view of a file system of data files, even though portions of the file system may be physically distributed between a client's own local storage, one or more file servers or even other client workstations.. These network file system mechanisms operate to hide the distinction between local data files and data files in the remotely distributed portions of the file system accessible only through the network. The advantages of such file system mechanisms include retention of multi-user access controls over the data files physically present on the server, to the extent intrinsically provided by a server, and a substantial simplification of a client workstation's view and productive utilization of the file system. Two implementations of a network file system mechanism are known as the network file system (NFS), available from Sun Microsystems, Inc. , and the remote file sharing (RFS) system available from American Telephone and Telegraph, Inc. The immediate consequence of network file system mechanism is that they have served to substantially increase the throughput requirements of the file server itself, as well as that of the communications network. Thus, the number of client workstations that can be served by a single file server must be balanced against the reduction in productivity resulting from increased file access response time and the potentially broader effects of a degradation in communication efficiency due to the network operating at or above its service maximum. An increase in the number of client workstations is conventionally handled by the addition of another file server, duplicating or possibly partitioning the file system between the file servers, and providing a dedicated high bandwidth network connection between the file servers. Thus, another consequence of the limited throughput of conventional file servers is a greater cost and configuration complexity of the file server base in relation to the number of client workstations that can be effectively serviced. Another complicating factor, for many technical and practical reasons, is a requirement that the file server be capable of executing the same or a similar operating system as the attached client workstations. The reasons include the need to execute maintenance and monitoring programs on the file server, and to execute programs, such as database servers, that would excessively load the communications network if executed remotely from the required file data. Another often overlooked consideration is the need to avoid the cost of supporting an operating system that is unique to the file server. Given these considerations, the file server is typically only a conventional general purpose computer with an extended data storage capacity and communications network interface that is little different from that present on each of the client workstations. Indeed, many file servers are no more than a physically repackaged workstation. Unfortunately, even with multiple communications network interfaces, such workstation-based computers are either incapable or inappropriate, from a cost/performance viewpoint, to perform as a single file server to a large group of client workstations. The throughput offered by conventional general purpose computers, considered in terms of their sustained file system facility data transfer bandwidth potential, is limited by a number of factors, though primarily due to the general purpose nature of their design. Computer system design is necessarily dependent on the level and nature of the operating system to be executed, the nature of the application load to be executed, and the degree of homogeneity of applications. For example, a computer system utilized solely for scientific computations may forego an operating system entirely, may be restricted to a single user at a time, and employ specialized computation hardware optimized for the anticipated highly homogeneous applications. Conversely, where an operating system is required, the system design typically calls for the utilization of dedicated peripheral controllers, operated under the control of a single processor executing the operating system, in an effort to reduce the peripheral control processing overhead of the system's single primary processor. Such is the design of most conventional file servers. A recurring theme in the design of general purpose computer systems is to increase the number of active primary processors. In the simplest analysis, a linear improvement in the throughput performance of the computer system might be expected. However, utilization of increasing numbers of primary processors is typically thwarted by the greater growth of control overhead and contention for common peripheral resources. Indeed, the net improvement in throughput is often seen to increase slightly before declining rapidly as the number of processors is increased. Summary of the Invention: Therefore, a general purpose of the present invention is to provide an operating system architecture for the control of a multi-processor system to provide an efficient, expandable computer system for servicing network file system requests. This is achieved in a computer system employing a multiple facility operating system architecture. The computer system includes a plurality of processor units for implementing a predetermined set of peer-level facilities, wherein each peer-level facility implements a plurality of related functions, and a communications bus for interconnecting the processor units. Each of the processor units includes a central processor and a stored program that, upon execution, provides for the implementation of a predetermined peer-level facility and for implementing a multi-tasking interface function. The multi-tasking interface function is responsive to control messages for selecting for execution functions of the predetermined peer-level facility. The multi-tasking interface function is also responsive to the predetermined peer-level facility for providing control messages to request or to respond to the performance of functions of another peer-level facility of the computer system. The multi-tasking interface functions of each of the plurality of processor units communicate among one another via the network bus. Thus, in a preferred embodiment of the present invention, the set of peer-level facilities includes network communications, file system control, storage control and a local host operating system. An advantage of the present invention is that it provides for the implementation of multiple facilities, each instance on a respective processor, all within a single cohesive system while incurring little additional control overhead in order to maintain operational coherency. Another advantage of the present invention is that direct peer to peer-level facility communication is supported in order to minimize overhead in processing network file system requests. A further advantage of the present invention is that it realizes a computer system software architecture that is readily expandable to include multiple instances of each peer-level facility, and respective peer-level processors, in a single cohesive operating system environment including direct peer to peer-level facility communications between like facilities. Yet another advantage of the present invention is that it may include an operating system as a facility operating concurrently and without conflict with the otherwise independent peer to peer-level facility communications of the other peer-level facilities. The operating system peer-level facility may itself be a conventional operating system suitably compatible with the workstation operating systems so as to maintain compatibility with "standard" file server operating systems. The operating system peer-level facility may be used to handle exception conditions from the other peer-level facilities including handling of non-network file system requests. Consequently, tne multiple facility operating system architecture of the present invention appears to client workstations as a conventional, single processor file server. A still further advantage of the present invention is that it provides a message-based operating system architecture framework for the support of multiple, specialized peer-level facilities within a single cohesive computer system; a capability particularly adaptable for implementation of a high- performance, high-throughput file server. Brief Description of the Drawings: These and other attendant advantages and features of the present invention will become apparent and readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference numerals indicate like parts throughout the figures thereof, and wherein: Fig. 1 is a simplified block diagram of a preferred computer system architecture for implementing the multiple facility operating system architecture of the present invention; Fig. 2. is a block diagram of a network communications processor suitable for implementing a network communications peer-level facility in accordance with a preferred embodiment of the present invention; Fig. 3 is a block diagram of a file system processor suitable for implementing a file system controller peer-level facility in accordance with a preferred embodiment of the present invention; Fig. 4 is a block diagram of a storage processor suitable for implementing a storage peer-level facility in accordance with a preferred embodiment of the present invention; Fig. 5 is simplified block diagram of a primary memory array suitable for use as a shared memory store in a preferred embodiment of the present invention; Fig. 6 is a block diagram of the multiple facility operating system architecture configured in accordance with a preferred embodiment of the present invention; Fig. 7 is a representation of a message descriptor passed between peer-level facilities to identify the location of a message; Fig. 8 is a representation of a peer-level facility message as used in a preferred embodiment of the present invention; Fig. 9 is a simplified representation of a conventional program function call; Fig. 10 is a simplified representation of an inter-facility function call in accordance with the preferred embodiment of the present invention; Fig. 11 is a control state diagram illustrating the interface functions of two peer-level facilities in accordance with a preferred embodiment of the present invention; Fig. 12 is an illustration of a data flow for an LFS read request through the peer-level facilities of a preferred embodiment of the present invention; Fig. 13 is an illustration of a data flow for an LFS write request through the peer-level facilities of a preferred embodiment of the present invention; Fig. 14 illustrates the data flow of a non-LFS data packet between the network communication and local host peer-level facilities in accordance with a preferred embodiment of the present invention; and Fig. 15 illustrates the data flow of a data packet routed between two network communications peer-level facilities in accordance with a preferred embodiment of the present invention. Detailed Description of the Invention: While the present invention is broadly applicable to a wide variety of hardware architectures, and its software architecture may be represented and implemented in a variety of specific manners, the present invention may be best understood from an understanding of its preferred embodiment. J , System Acchj.tecti-.re Overvie Hardware Architecture Overview A block diagram representing the preferred embodiment of the hardware support for the present invention, generally indicated by the reference numeral 10, is provided in Fig 1. The architecture of the preferred hardware system 10 is described in the above-identified related application entitled PARALLEL I/O NETWORK FILE SERVER ARCHITECTURE; which application is expressly incorporated herein by reference. The hardware components of the system 10 include multiple instances of network controllers 12, file system controllers 14, and mass storage processors, 16, interconnected by a high-bandwidth backplane bus 22. Each of these controllers 12, 14, 16 preferably include a high performance processor and local program store, thereby minimizing their need to access the bus 22. Rather, bus 22 accesses by the controllers 12, 14, 16 are substantially limited to transfer accesses as required to transfer control information and client workstation data between the controllers 12, 14, 16 εyεtem memory 18, and a local host processor 20, when necessary. The illustrated preferred system 10 configuration includes four network controllers 12, ,, two file controllers 14, _, two mass storage processors 16 ι_ 2 ' a bank of four system memory cards 18 -, __, , and a host processor 20 coupled to the backplane bus 22. The invention, however, is not limited to this number and type of processors. Rather, six or more network communications processors 12 and two or more host processors 20 could be implemented within the scope of the present invention. Each network communications processor (NP) l 2 - ι _ 4 preferably includes a Motorola 68020 processor for supporting two independent Ethernet network connections, shown as the network pairs Each of the network connections directly support the ten megabit per second data rate specified for a conventional individual Ethernet network connection. The preferred hardware embodiment of the present invention thus realizes a combined maximum data throughput potential of 80 megabits per second. The file system processors (FP) 14.. _, intended to .operate primarily as a specialized compute engines, each include a high-performance Motorola 68020 based microprocessor, four megabytes of local data store and a smaller quarter-megabyte high-speed program memory store. The storage processors (SP) 16 ι _ function as intelligent small computer system interface (SCSI) controllers. Each includes a Motorola 68020 micro¬ processor, a local program and data memory, and an array of ten parallel SCSI channels. Drive arrays 24, ,. are coupled to the storage processors l 6 ι_ 2 ~° provide mass storage. Preferably, the drive arrays 24 ι- 2 are ten unit- ide arrays of SCSI storage devices uniformly from one to three units deep. The preferred embodiment of the present invention uses conventional 768 megabyte 5- -inch hard disk drives for each unit of the arrays 24, „. Thus, each drive array level achieves a storage capacity of approximately 6 gigabytes, with each storage processor readily supporting a total of 18 gigabytes. Consequently, a system 10 is capable of realizing a total combined data storage capacity of 36 gigabytes. The local host processor 20, in the preferred embodiments of the present invention, is a Sun central processor card, model Sun 3E120, manufactured and distributed by Sun Microsystems, Inc. Finally, the system memory cards 18 each provide 48 megabytes of 32-bit memory for shared use within the computer system 10. The memory is logically visible to each of the processors of the system 10. A VME bus 22 is used in the preferred embodiments of the present invention to interconnect the network communication processors 12, file system processors 14, storage processors 16, primary memory 18, and host processor 20. The hardware control logic for controlling the VME bus 22, at least as implemented on the network communication processor 12 and storage processor 16, implements a bus master fast transfer protocol in addition to the conventional VME transfer protocols. The system memory 18 correspondingly implements a modified slave VME bus control logic to allow the system memory 18 to also act as the fast data transfer data source or destination for the network communication processors 12 and storage processors 16. The fast transfer protocol is described in the above- identified related application entitled "ENHANCED VMEBUS PROTOCOL UTILIZING SYNCHRONOUS HANDSHAKING AND BLOCK MODE DATA TRANSFER"; which application is expressly incorporated herein by reference. It should be understood that, while the system 10 configuration represents the initially preferred maximum hardware configuration, the present invention is not limited to the preferred number or type of controllers, the preferred size and type of disk drives or use of the preferred fast data transfer VME protocol. B. Software Architecture Overview Although applicable to a wide variety of primary, or full function, operating systems such as MVS and VMS, the preferred embodiment of the present invention is premised on the Unix operating system as distributed under license by American Telephone and Telegraph, Inc. and specifically the SunOS version of the Unix operating system, as available from Sun Microsystems, Inc. The architecture of the Unix operating system has been the subject of substantial academic study and many published works including "The Design of the Unix Operating System", Maurice J. Bach, Prentice Hall, Inc. , 1986. In brief, the Unix operating system is organized around a non-preemptive, multi-tasking, multi-user kernel that implements a simple file-oriented conceptual model of a file system. Central to the model is a virtual file system (VFS) interface that operates to provide a uniform file oriented, multiple file system environment for both local and remote files. Connected to the virtual file system is the Unix file system (UFS). The UFS allows physical devices, pseudo-devices and other logical devices to appear and be treated, from a client's perspective, as simple files within the file system model. The UFS interfaces to the VFS to receive and respond to file oriented requests such as to obtain the attributes of a file, the stored parameters of a physical or logical device, and, of course, to read and write data. In carrying out these functions, the UFS interacts with a low level software device driver that is directly responsible for an attached physical mass storage device. The UFS handles all operations necessary to resolve logical file oriented operations, as passed from the VFS, down to the level of a logical disk sector read or write request. The VFS, in order to integrate access to remote files into the file system model, provides a connection point for network communications through the network file system mechanism, if available. The preferred network file system mechanism, NFS, is itself premised on the existence of a series of communication protocol layers that, inclusive of NFS and within the context of the present invention, can be referred to as an NFS stack. These layers, in addition to an NFS "layer," typically include a series of protocol handling layers generally consistent with the International Standards Organization's Open Systems Interconnection (ISO/OSI) model. The OSI model has been the subject of many publications, both regarding the conceptual aspects of the model as well as specific implementations, including "Computer Networks, 2nd Edition", Andrew S. Tanenbaum, Prentice Hall, 1988. In summary, the OSI layers utilized by the present invention include all seven layers described in the OSI reference model: application, presentation, session, transport, network, data link and physical layers. These layers are summarized below, in terms of their general purpose, function and implementation for purposes of the present invention. The application layer protocol, NFS, provides a set of remote procedure -call definitions, for use in both server and client oriented contexts, to provide network file services. As such, the NFS layer provides a link between the VFS of the Unix kernel and the presentation protocol layer. The presentation layer protocol, provided as an external data representation (XDR) layer, defines a common description and encoding of data as necessary to allow transfer of data between different computer architectures. The XDR is thus responsible for syntax and semantic translation between the data representations of heterogeneous computer systems. The session layer protocol, implemented as a remote procedure call (RPC) layer, provides a remote procedure call capability between a client process and a server process. In a conventional file server, the NFS layer connects through the XDR layer to the RPC layer in a server context to support the file oriented data transfers and related requests of a network client. The transport layer protocol, typically implemented as either a user datagram protocol (UDP) or transmission control protocol (TCP) layer, provides for a simple connectionless datagram delivery service. NFS uses UDP. The network layer protocol, implemented as an internet protocol (IP) layer, performs internet routing, based on address mappings stored in an IP routing database, and data packet fragmentation and reassembly. The data link (DL) layer manages the transfer and receipt of data packets based on packet frame information. Often this layer is referred to as a device driver, since it contains the low level software control interface to the specific communications hardware, including program control of low level data transmission error correction/handling and data flow control. As such, it presents a hardware independent interface to the IP layer. Finally, the physical layer, an Ethernet controller, provides a hardware interface to the network physical transmission medium. The conventional NFS stack, as implemented for the uniprocessor VAX architecture, is available in source code form under license from Sun Microsystems, Inc. The preferred embodiment of the present invention utilizes the conventional SunOS Unix kernel, the Sun/VAX reference release of the UFS, and the Sun/VAX reference release of the NFS stack as its operating system platform. The present invention establishes an instantiation of the NFS stack as an independent, i.e., separately executed, software entity separate from the Unix kernel. Instantiations of the UFS and the mass storage device driver are also established as respective independent software entities, again separate from the Unix kernel. These entities, or peer-level facilities, are each provided with an interface that supports direct communication between one another. This interface, or messaging kernel layer, includes a message passing, multi-tasking kernel. The messaging kernel's layers are tailored to each type of peer-level facility in order to support T/US90/047 -22- the specific facility's functions. The provision for multi-tasking operation allows the peer-level facilities to manage multiple concurrent processes. Messages are directed to other peer-level facilities based upon the nature of the function requested. Thus, for NFS file system requests, request messages may be passed from an NFS network communications peer-level facility directly to a UFS file system peer-level facility and, as necessary, then to the mass storage peer-level facility. The relevant data path is between the NFS network communications peer-level facility and the mass storage peer-level facility by way of the VME shared address space primary memory. Consequently, the number of peer-level facilities is not logically bounded and servicing of the most common type of client workstation file system needs is satisfied while requiring only a minimum amount of processing. Finally, a Unix kernel, including its own NFS stack, UFS, and mass storage device driver, is established as a another peer-level facility. As with the other peer-level facilities, this operating system facility is provided with a multi-tasking interface for interacting concurrently with the other peer-level facilities as just another entity within the system 10. While the operating system kernel peer-level facility is not involved in the immediate servicing of most NFS requests, it interacts with the NFS stack peer-level facility to perform general management of the ARP and IP data bases, the initial NFS file system access requests from a client workstation, and to handle any non-NFS type requests that might be received by the NFS stack peer-level facility. XL Peer-leyel rocessors A. Network Control Processor A block diagram of the preferred network control processor is shown in Fig. 2. The network controller 12 includes a 32-bit central processing unit (CPU) 30 coupled to a local CPU bus 32 that includes address, control and data lines. The CPU is preferably a Motorola 68020 processor. The data line portion of the CPU bus 32 is 32 bits wide. All of the elements coupled to the local bus 32 of the network controller 12 are memory mapped from the perspective of the CPU 30. This is enabled by a buffer 34 that connects the local bus 32 to a boot PROM 38. The boot PROM 38 is utilized to store a boot program and its necessary start-up and operating parameters. Another buffer 40 allows the CPU 30 to separately address a pair of Ethernet local area network (LAN) controllers 42, 44, their local data packet memories 46, 48, and their associated packet direct memory access (DMA) controllers 50, 52, via two parallel address, control, and 16-bit wide data buses 54, 56. The LAN controllers 42, 44 are programmed by the CPU 30 to utilize their respective local buffer memories 46, 48 for the storage and retrieval of data packets as transferred via the Ethernet connections 26. The DMA controllers 50, 52 are programmed by the CPU 30 to transfer data packets between the buffer memories 46, 48 and a respective pair of multiplexing FIFOs 58, 60 also connected to the LAN buses 54, 56. The multiplexing FIFOs 58, 60 each include a 16-bit to 32-bit wide data multiplexer/demultiplexer, coupled to the data portion of the LAN buses 54, 56, and a pair of internal FIFO buffers. Thus, for example in the preferred embodiment of the present invention, a first 32-bit wide internal FIFO is coupled through the multiplexer to the 16-bit wide LAN bus 54. The second internal FIFO, also 32-bit wide, is coupled to a secondary data bus 62. These internal FIFO buffers of the multiplexing FIFO 58, as well as those of the multiplexing FIFO 60, may be swapped between their logical connections to the LAN buses, 54, 56 and the secondary data bus 62. Thus, a large difference in the data transfer rate of the LAN buses 54, 60 and the secondary data bus 62 can be maintained for a burst data length equal to the depth of the internal FIFOs 58, 60. A high speed DMA controller 64, controlled by the CPU 30, is provided to direct the operation of the multiplexing FIFOs 58, 60 as well as an enhanced VME control logic block 66, through which the data provided on the secondary data bus 62 is communicated to the data lines of the VME bus 22. The purpose of the multiplexing FIFOs 58, 60, besides acting as a 16-bit to 32-bit multiplexer and buffer, is to ultimately support the data transfer rate of the fast transfer mode of the enhanced VME control logic block 66. Also connected to the local CPU data bus 32 is a quarter megabyte block of local shared memory 68, a buffer 70, and a third multiplexing FIFO 74. The memory 68 is shared in the sense that it also appears within the memory address space of the enhanced VME bus 22 by way of the enhanced VME control logic block 66 and buffer 70. The buffer 70 preferably provides a bidirectional data path for transferring data between the secondary data bus 62 and the local CPU bus 32 and also includes a status register array for receiving and storing status words either from the CPU 30 or from the enhanced VME bus 22. The multiplexing FIFO 74, identical to the multiplexing FIFOs 58, 60, provides a higher speed, block-oriented data transfer capability for the CPU 30. Finally, a message descriptor FIFO 72 is connected between the secondary data bus 62 and the local CPU bus 32. Preferably, the message descriptor FIFO 72 is addressed from the enhanced VME bus 22 as a single shared memory location for the receipt of message descriptors. Preferably the message descriptor FIFO 72 is 32-bit wide, single buffer FIFO with a 256-word storage capability. In accordance with the preferred embodiments of the present invention, the message descriptor FIFO is described in detail in the above- referenced related application "BUS LOCKING FIFO MULTI-PROCESSOR COMMUNICATIONS SYSTEM"; which application is hereby incorporated by reference. However, for purposes of completeness, an enhancement embodied in the enhanced VME control logic block 66 is that it preemptively allows writes to the message descriptor FIFO 72 from the enhanced VME bus 22 unless the FIFO 72 is full. Where a write to the message descriptor FIFO 72 cannot be accepted, the enhanced VME control logic block 66 immediately declines the write by issuing a VME bus error signal onto the enhanced VME bus. B. File System Control Processor The preferred architecture of a file system processor 14 60 is shown in Fig. 3. A CPU 80, preferably a Motorola 68020 processor, is connected via a local CPU address, control and 32-bit wide data bus 82 to the various elements of the file controller 14. These principle elements include a 256 kilobytes of static RAM block 84, used for storing the file system control program, and a four megabyte dynamic RAM block 86 for storing local data, both connected directly to the local CPU bus 82. A buffer 88 couples the local CPU bus 82 to a secondary 32-bit wide data bus 90 that is, in turn, coupled through an enhanced VME control and logic block 92 to the data bus lines of the VME bus 22. In addition to providing status register array storage, the buffer 88 allows the memory blocks 84, 86 to be accessible as local shared memory on the VME bus 22. A second buffer 94 is provided to logically position a boot PROM 96, containing the file controller initialization program, within the memory address map of the CPU 80. Finally, a single buffer message descriptor FIFO 98 is provided between the secondary data bus 90 and the local CPU bus 82. The message descriptor FIFO 98 is again provided to allow preemptive writes to the file controller 14 from the enhanced VME bus 22. C. Storage Control Processor A block diagram of a storage processor 16 is provided in Fig. 4. A CPU 100, preferably a Motorola 68020 processor, is coupled through a local CPU address, control and 32-bit wide data bus 102 and a buffer 104 to obtain access to a boot PROM 106 and a double-buffered multiplexing FIFO 108 that is, in turn, connected to an internal peripheral data bus 110. The internal peripheral data bus 110 is, in turn, coupled through a parallel channel array of double-buffered multiplexing FIFOs 112, 10 and SCSI channel controllers 114_.__,_. The SCSI controllers 114, .. support the respective SCSI buses (SCSI0 - SCSI9) that connect to a drive array 24. Control over the operation of the double buffer FIFO 112. , and SCSI controller 114 ι _ ιn arrays is ultimately by the CPU 100 via a memory-mapped buffer 116 and a first port of a dual ported SRAM command block 118. The second port of the SRAM block 118 is coupled to a DMA controller 120 that controls the low level transfer of data between the double-buffered FIFOs 108, 112- ,-, a temporary store buffer memory 122 and the enhanced VME bus 22. In accordance with a preferred embodiment of the present invention, the DMA controller responds to commands posted by the CPU 100 in the dual-ported SRAM block 118 to select any of the double-buffered FIFOs 108, 112, 10 , the buffer memory 122, and the enhanced VME bus 22 as a source or destination of a data block transfer. To accomplish this, the DMA controller 120 is coupled through a control bus 124 to the double buffered FIFOs 108, 112^ _._, the SCSI controllers 114. ιn , the buffer memory 122, a pair of secondary data bus buffers 126, 128, and an enhanced VME control and logic block 132. The buffers 126, 128 are used to route data by selectively coupling the internal peripheral data bus 110 to a secondary data bus 130 and the buffer memory 122. The DMA controller 120, as implemented in accordance with a preferred embodiment of the present invention, is described in detail in the above-referenced related application "IMPROVED FAST TRANSFER DIRECT MEMORY ACCESS CONTROLLER"; which application is hereby incorporated by reference. Finally, a one megabyte local shared memory block 134, a high speed buffer and register array 136, and a preemptive write message descriptor FIFO 138 are provided connected directly to the local CPU data bus 102. The buffer 136 is also coupled to the secondary data bus 130, while the message descriptor FIFO 138 is coupled to the secondary data bus 130. D. Primary Memory Array Fig. 5 provides a simplified block diagram of the preferred architecture of a memory card 18. Each memory card 18 operates as a slave on the enhanced VME bus and therefore requires no on-board CPU. Rather, a timing control block 150 is sufficient to provide the necessary slave control operations. In particular, the timing control block 150, in response to control signals from the control portion of the enhanced VME bus 22 enables a 32-bit wide buffer 152 for an appropriate direction transfer of 32-bit data between the enhanced VME bus 22 and a multiplexer unit 154. The multiplexer 154 provides a multiplexing and demultiplexing function, depending on data transfer direction, for a six megabit by seventy-two bit word memory array 156. An error correction code (ECC) generation and testing unit 158 is coupled to the multiplexer 154 to generate or verify, again depending on transfer direction, eight bits of ECC data per memory array word. The status of each ECC verification operation is provided back to the timing control block 150. E. Host Processor The host processor 20, as shown in Fig. 1, is a conventional Sun 3E120 processor. Due to the conventional design of this product, a software emulation of a message descriptor FIFO is performed in a reserved portion of the local host processor's shared memory space. This software message descriptor FIFO is intended to provide the functionality of the message descriptor FIFOs 72, 98, and 138. A preferred embodiment of the present invention includes a local host processor 20', not shown, that includes a hardware preemptive write message descriptor FIFO, but that is otherwise functionally equivalent to the processor 20. in, peer-level Facility Architecture A. Peer-Level Facility Functions Fig. 6 provides an illustration of the multiple peer-level facility architecture of the present invention. However, only single instantiations of the preferred set of the peer-level facilities are shown for purposes of clarity. The peer-level facilities include the network communications facility (NC) 162, file system facility (FS) 164, storage facility (S) 166 and host facility (H) 168. For completeness, the memory 18 is illustrated as a logical resource 18' and, similarly, the disk array 24 as a resource 24'. The network communications facility 162 includes a messaging kernel layer 178 and an NFS stack. The messaging kernel layer 178 includes a multi-tasking kernel that supports multiple processes. Logically concurrent executions of the code making up the NFS stack are supported by reference to the process context in which execution by the peer-level processor is performed. Each process is uniquely identified by a process ID (PID) . Context execution switches by the peer-level processor are controlled by a process scheduler embedded in the facility's multi-tasking kernel. A process may be "active" — at a minimum, where process execution by the peer-level processor continues until a resource or condition required for continued execution is unavailable. A process is "blocked" when waiting for notice of availability of such resource or condition. For the network communications facility 162, within the general context of the present invention, the primary source of process blocking is in the network and lower layers where a NC process will wait, executing briefly upon receipt of each of a series of packet frames, until sufficient packet frames are received to be assembled into a complete datagram transferrable to a higher level layer. At the opposite extreme, a NC process will block upon requesting a file system or local host function to be performed, i.e., any function controlled or implemented by another peer-level facility. The messaging kernel layer 178, like all of the messaging kernel layers of the present invention, allocates processes to handle respective communication transactions. In allocating a process, the messaging kernel layer 178 transfers a previously blocked process, from a queue of such processes, to a queue of active processes scheduled for execution by the multi¬ tasking kernel. At the conclusion of a communication transaction, a process is deallocated by returning the process to the queue of blocked processes. As a new communication transaction is initiated, an address or process ID of an allocated process becomes the distinguishing datum by which the subsequent transactions are correlated to the relevant, i.e., proper handling, process. For example, where a client workstation initiates a new communication transaction, it provides its Ethernet address. The network communication facility, will store and subsequently, in responding to the request, utilize the client's Ethernet address to direct the response back to the specific requesting client. The NC facility similarly provides a unique facility ID and the PID of its relevant process to another peer-level facility as part of any request necessary to complete a client's request. Thus, an NC facility process may block with certainty that the responding peer-level facility can direct its response back to the relevant process of the network communications peer-level facility. The network and lower level layers of the NFS stack necessary to support the logical Ethernet connections 26' are generally illustrated together as an IP layer 172 and data link layer 170. The IP layer 172, coupled to the IP route database 174, is used to initially distinguish between NFS and non-NFS client requests. NFS requests are communicated to an NFS server 176 that includes the remaining layers of the NFS stack. The NFS server 176, in turn, communicates NFS requests to the network communications messaging kernel layer 178. By the nature of the call, the messaging kernel layer 178 is able to discern between NFS request calls, non-NFS calls from the IP layer 172 and network calls received directly from the network layers 170. For the specific instance of NFS requests, making up the large majority of requests handled by the network communications facility 162, the relevant NC process calls the messaging kernel layer 178 to issue a corresponding message to the messaging kernel layer 180 of the file system facility 164. The relevant NC process is blocked pending a reply message and, possibly, a data transfer. That is, when the messaging kernel layer 178 receives the NFS request call, a specific inter-facility message is prepared and passed to the messaging kernel layer 180 with sufficient information to identify the request and the facility that sourced the request. As illustrated, messages are exchanged between the various messaging kernel layers of the system 160. However, the messages are in fact transferred physically via the enhanced VME bus connecting the peer-level processors upon which the specific peer-level facilities are executing. The physical to logical relationship of peer-level facilities to peer-level processors is established upon the initialization of the system 160 by providing each of the messaging kernel layers with the relevant message descriptor FIFO addresses of the peer-level processors. In response to a message received, the messaging kernel layer 180 allocates a FS process within its multi-tasking environment to handle the * communication transaction. This active FS process is used to call, carrying with it the received message contents, a local file system (LFS) server 182. This LFS server 182 is, in essence, an unmodified instantiation 184 of the UFS. Calls, in turn, issued by this UFS 182, ultimately intended for a device driver of a mass storage device, are directed back to the messaging kernel layer 180. The messaging kernel layer distinguishes such device driver related functions being requested by the nature of the function call. The messaging kernel layer 180 blocks the relevant FS process while another inter-processor message is prepared and passed to a messaging kernel layer 186 of the storage facility 166. Since the storage facility 166 is also required to track many requests at any one time, a single manager process is used to receive messages. For throughput efficiency, this S manager process responds to FIFO interrupts, indicating that a corresponding message descriptor has just been written to the SP FIFO, and immediately initiates the SP processor operation necessary to respond to the request. Thus, the currently preferred S facility handles messages at interrupt time and not in the context of separately allocated processes. However, the messaging kernel layer 186 could alternately allocate an S worker process to service each received message request. The message provided from the file system facility 164 includes the necessary information to specify the particular function required of the storage facility in order to satisfy the request. Within the context of the allocated active S process, the messaging kernel layer 186 calls the request corresponding function of a device driver 188. Depending on the availability and nature of the resource requested, the device driver 188 will, for example, direct the requested data to be retrieved from the disk array resource 24'. As data is returned via the device driver layer 188, the relevant S process of the messaging kernel layer 186 directs the transfer of the data into the memory resource 18'. In accordance with the preferred embodiments of the present invention, the substantial bulk of the memory resource 18' is managed as an exclusive resource of the file system facility 164. Thus, for messages requesting the transfer of data to or from the disk array 24', the file system facility 164 provides an appropriate shared memory address referencing a suitably allocated portion of the memory resource 18' . Thus, as data is retrieved from the disk array 24', the relevant S process of the messaging kernel layer 186 will direct the transfer of data from the device driver layer 188 to the message designated location within the memory resource 18', as illustrated by the data path 190. Once the data transfer is complete, the relevant S process "returns" to the messaging kernel layer 186 and a reply message is prepared and issued by the messaging kernel layer 186 to the messaging kernel layer 180. The relevant S process may then be deallocated by the messaging kernel layer 186. In response to this reply message, the messaging kernel layer 180 unblocks its relevant FS process, i.e., the process that requested the S facility data transfer. This, in turn, results in the relevant FS process executing the UFS 182 and eventually issuing a return to the messaging kernel layer .180 indicating that the requested function has been completed. In response, the messaging kernel layer 180 prepares and issues a reply message on behalf of the relevant FS process to the messaging kernel layer 178; this message will include the shared memory address of the requested data as stored within the memory resource 18'. The messaging kernel layer 178 responds to the reply message from the file system facility 164 by unblocking the relevant NC process. Within that NC process's context, the messaging kernel layer 178 performs a return to the NFS server 176 with the shared memory address. The messaging kernel layer 178 -WPl/GBR/ΛUθr/7210.001 OQ/08/8»-g- At- y, Dockot No. : AUSP7 10MCr/GBR transfers the data from the memory resource 18' via the indicated data path 192 to local stored memory for use by the NFS server layer 176. The data may then be processed through the NFS server layer 176, IP layer 172 and the network and lower layers 170 into packets for provision onto the network 26' and directed to the originally requesting client workstation. Similarly, where data is received via the network layer 170 as part of an NFS write transfer, the data is buffered and processed through the NFS server layer 176. When complete, a call by the NFS server 176 to the messaging kernel layer 178 results in the first message of an inter-facility communication transaction being issued to the file system facility 164. The messaging kernel layer 180, on assigning a FS process to handle the request message, replies to the relevant NC process of the messaging kernel layer 178 with an inter-facility message containing a shared memory address within the memory resource 18'. The NFS data is then transferred from local shared memory via the data path 192 by the messaging kernel 178. When this data transfer is complete, another inter-facility message is passed to the relevant FS process of the messaging kernel layer 180. That process is then unblocked and processes the data transfer request through the LFS/UFS 182. The UFS 182, in turn, initiates, as needed, inter-facility communication transactions through the messaging kernel layer 180 to prepare for and ultimately transfer the data from the memory resource 18' via the data path 190 and device driver 188 to the disk array resource 24'. The host operating system facility 168 is a substantially complete implementation of the SunOS operating system including a TCP/IP and NFS stack. A messaging kernel layer 194, not unlike the messaging kernel layers 178, 180, 186 is provided to logically integrate the host facility 186 into the system 160. The operating system kernel portion of the facility 168 includes the VFS 196 and a standard instantiation of the UFS 198. The UFS 198 is, in turn, coupled to a mass storage device driver 200 that, in normal operation, provides for the support of UFS 198 requests by calling the messaging kernel layer 194 to issue inter-facility messages to the storage facility 166. Thus, the storage facility 166 does not functionally differentiate between the local host facility 168 and the file system facility 164 except during the initial phase of bootup. Rather, both generally appear as unique but otherwise undifferentiated logical clients of the storage facility 166. Also interfaced to the VFS 196 is a conventional client instantiation of an NFS layer 202. That is, ■WP1/GDR/AUG-P/7 10.001 ,00/08/89 C fcty. Dor at Nn • ΛUSr7210MCF/GBg- the NFS layer 202 is oriented as a client for processing client requests directed to another file server connected through a network communications facility. These requests are handled via a TCP/UDP layer 204 of a largely conventional instantiation of the Sun NFS client stack. Connected to the layer 204 are the IP and data link layers 206. The IP and data link layers 206 are modified to communicate directly with the messaging kernel layer 194. Messages from the messaging kernel layer 194, initiated in response to calls directly from the data link layer 206 are logically directed by the messaging kernel 178 directly to the data link layer 170 of a network communications facility. Similarly, calls from the IP layer 172, recognized as not NFS requests of a local file system, are passed through the messaging kernel layers 178 and 194 directly to the TCP/UDP layers 204. In accordance with the preferred embodiments of the present invention, the responses by the host facility 168 in such circumstances are processed back through the entire host TCP/IP stack 214, 204, 206, the messaging kernel layers 194, 178, and finally the data link layer 170 of an NC facility 162. Ancillary to the IP and data link layers 206, a route database 208 is maintained under the control and direction of a conventional "routed" daemon application. This, and related daemons such as the "mountd" , execute in the application program layer as background processes. In order to maintain coherency between the route database 208 and the route database 174 present in the network communications facility 162, a system call layer 212, provided as the interface between the application program layer and the kernel functions of the host facility 168, is modified in accordance with the present invention. The modification provides for the issuance of a message containing any update information directed to the route database 208, from the daemons, to be provided by an inter-facility communication transaction from the messaging kernel layer 194 to the messaging kernel layer 178. Upon receipt of such a message, the messaging kernel layer 178 directs an appropriate update to the route database 174. The system call layer 212 also provides for access to the TCP/UDP layers via a conventional interface layer 214 known as sockets. Low level application programs may use the system call layer 212 to directly access the data storage system by calling directly on the device driver 200. The system call layer also interfaces with the VFS 196 for access to or by the NFS client 202 and the UFS 198. In addition, as provided by the preferred embodiments of the present invention, the VFS 196 also interfaces to a local file system (LFS) client layer 216. The conventional VFS 196 implements a "mount" model for handling the logical relation between and access to multiple file systems. By this model a file system is mounted with respect to a specific file system layer that interfaces with the VFS 196. The file system is assigned a file system ID (FSID) . File operations subsequently requested of the VFS 196 with regard to a FSID identified file system will be directed to the appropriate file system. In accordance with the present invention, the LFS. client layer 216 is utilized in the logical mounting of file systems mounted through the file system facility 164. That is, the host facility's file oriented requests presented to the VFS 196 are routed, based on their FSID, through the LFS client layer 216 to the messaging kernel layer 194, and, in turn, to the messaging kernel layer 180 of the file system facility 164 for servicing by the UFS 182. The model is extended for handling network file system requests. A client workstation may then issue a mount request for a file system previously exported through the VFS 196. The mount request is forwarded by a network communications facility 162 ultimately to a mounted -44- daemon running in the application layer 210 of the host facility 194. The mounted daemon response in turn provides the client with the FSID of the file system if the export is successful. Thereafter, the client's NFS file system requests received by the network communications facility 162 will be redirected, based on the FSID provided with the request, to the appropriate file system facility 164 that has mounted the requested file system. Consequently, once a file system is mounted by the UFS 182 and exported via the network communications and host facilities 162, 168, file oriented NFS requests for that file system need not be passed to or processed by the host facility 168. Rather, such NFS requests are expediently routed directly to the appropriate file system facility 164. The primary benefits of the present invention should now be apparent. In addition to allowing multiple, independent instantiations of the network communication, file system, storage and host facilities 162, 164, 166, 168, the immediate requirements for all NFS requests may be serviced without involving the substantial performance overhead of the VFS 196 and higher level portions of the conventional Unix operating system kernel. Finally, another aspect of the host facility 168 is the provision for direct access to the messaging kernel layer 194 or via the system call layer 212 as appropriate, by maintenance application programs when executed within the application program layer 210. These maintenance programs may be utilized to collect performance data from status accumulation data structures maintained by the messaging kernel layer 194 and, by utilizing corresponding inter-facility messages, the accumulated status information from status data structures in the messaging kernel layers 178, 180 and 186. B. Messaging Kernel Layer Functions The messaging kernel layers 178, 180, 186 and 194 each include a small, efficient multi-tasking kernel. As such, it provides only fundamental operating system kernel services. These services include simple lightweight process scheduling, message passing and memory allocation. A library of standard functions and processes provide services such as sleep(), wakeupO, error logging, and real time clocks in a manner substantially similar to those functions of a conventional Unix kernel. The list below summarizes the primary function primitiveε of the multi-tasking kernel provided in each of the messaging kernel layers 178, 180-, 186 and 194. k_register(name) Registers the current process as a provider of a named service. k_resolve(name) Returns the process ID for a named service. k_εend(msg,pid) Sends a message to a specified process and blocks until the message is returned. k_reply(msg) Returns a received messages to its sender. k_null_reply(msg) Returns an unmodified message to the sender. (Faster than k_reply(msg) because the message need not be copied back. ) k receive() Blocks until a message is sent to this process. The balance of the mesεaging kernel layers 178, 180, 186 and 194 is made up of routines that presumptively implement, at least from the perspective of the balance of the facility, the functions that a given facility might request of another. These routines are premised on the function primitives provided by the multi-tasking kernel to provide the specific interface functions necessary to support the NFS stack, UFS, storage device driver, or host operating system. Since such routines do not actually perform the functions for which they are called, they may be referred to as "stub routines". C. Tnter-Facilitv Communication HFC) System Communication or information between the peer- level facilities ic performed as a series of communication transactions. Λ transaction, defined as a request message and a reply message, occurs between a pair of messaging kernel layers, though others may "listen" in order to gather performance data or perform diagnostics. A single transaction may be suspended, i.e.., the reply message held, while the receiving messaging kernel layer initiates a β parate communication transaction with another peer-level facility. Once the reply message of the second transaction is received, a properly reply to the initial communication transaction can then be made. .]_____. Me B sar-s-Dsscri-ptors an a Messages The transfer of a message between sending and receiving messaging kernel layers is, in turn, generally a two step process. The first step ib for the sending messaging kernel layer to write a message descriptor to the receiving messaging kernel layer. This is accomplished by the message descriptor being written to the descriptor FIFO of the receiving peer- level processor. The second step is for the message, as identified by the message descriptor, to be copied, either actually or implicitly, from the sending messaging kernel layer to the receiving messaging kernel layer. This copy, when actually performed, is a memory to memory copy from the shared memory space of the sending peer-level processor to that of the receiving peer- level processor. Depending on the nature of the communication transaction, the message copy will be actually performed by the sending or receiving peer- level processor, or implicitly by reference to the image of the original message kept by the messaging kernel layer that initiated a particular communication transaction. The message identified by a message descriptor is evaluated by the receiving messaging kernel layer to determine what is to be done with the message. A message descriptor as used by a preferred embodiment of the present invention is shown in Fig. 7. The message descriptor is, in essence, a single 32-bit word partitioned into, two fields. The least significant field is used to store a descriptor modifier, while the high order 30-bit field provides a shared memory address to a message. The preferred values of the modifier field are given in Table 1. Table 1 Message Modifiers Modifier Meaning 0 Pointer to a message being sent 1 Pointer to a reply message 2 Pointer to message to be forwarded 3 Pointer to message acknowledging a forwarded message For request messages that are being sent, the receiving messaging kernel layer performs the message copy. For a message that is a reply to a prior message, the sending messaging kernel layer is effectively told whether a message copy must be performed. That is, where the contents of a message have not been changed by the receiving messaging kernel layer, an implicit copy may be performed by replying with a messaging descriptor that points to the original message image within the sending messaging kernel layer's local shared memory space. Similarly for forwarding type communication transactions the receiving messaging kernel layer performs the copy. A message forwarding transaction is completed when an acknowledgement message is provided. The purpose of the acknowledgement is to notify the sending messaging kernel layer to know that it can return the reference message buffer to its free buffer pool. The preferred block format of a message is illustrated in Fig. 8. The message is a single data εtruσture defined to occupy 128 bytes. The initial 32-bit word of the message encodes the message type and a unique peer-level facility identifier. The text of the message then follows with any necessary fill to reach a current maximum text limit. In the preferred embodiment of the present invention, the text length is 84 bytes. An inter-facility communication (IFC) control data block is provided, again followed by any necessary fill characters needed to complete the 128- byte long message. This IFC control data preferably includes a copy of the address of the original message, the relevant sending and receiving (destination) process identifiers associated with the current message, and any queue links required to manage the structure while in memory. An exemplary message structure is provided in Table 2. Table 2 Exemplary Message Structure typedef struct ml6_msg { K_MSGTYPE type; /* request code */ char msg[84] ; vme t addr; /* shared memory address of the original message */ PID ml6_sender_ id; /* PID of last sender. */ PID ml6_forward_jpid;/* PID of last forwarder. */ PID ml6_dest_pid; /* PID of deεt. process. */ /* Following value is LOCAL and need not be transferred. */ struct ml6_msg *ml6_link; /* message queue link */ } K MSG; This structure (K_MSG) includes the message type field (K_MSGTYPE) , the message text (rnsgU), and the IFC block (addr, ml6_sender_pid, ml6_sender_ id, ml6_dest_pid, and ml6_link) . This K_MSG structure is used to encapsulate specific messages, such as exemplified by a file system facility message structure (FS STD T) shown in Table 3. Table 3 Exemplary Specific Message Structure /* Access credentials */ /* File handle */ /* For fc_get_server. */ /* {READ,WRITE,EXEC} for fc_access. */ /* FS facility server pid /* Mask attributes. */ The FS_STD_T structure is overlaid onto a K_MSG structure with byte zero of both structures aligned. This composite message structure is created as part of the formatting of a message prior to being sent. Other message structures, appropriate for particular message circumstances, may be used. However, all are consistent with the use of the K_MSG message and block format described above. 2. IFC Message Generation The determination to send a message, and the nature of the message, is determined by the peer-level facilities. In particular, when a process executing on a peer-level processor requires the support of another peer-level facility, such as to store or retrieve data or to handle some condition that it alone cannot εervice, the peer-level facility issues a message requesting the required function or support. This message, in accordance with the present invention, is generally initiated in response to the same function call that the facility would make in a uniprocessor configuration of the prior art. That is, in a conventional single processor software system, execution of a desired function may be achieved by calling an appropriate routine, that, in turn, determines and calls its own service routines. This is illustrated in Fig. 9. A function call to a routine A, illustrated by the arrow 300, may select and call 302 a routine B. As may be necessary to carry out its function, the routine B may call 304 still further routines. Ultimately, any functions called by the routine B return to the function B which returns to the function A. The function A then itself returns with the requested function call having been completed. In accordance with the present invention, the various messaging kernels layers have been provided to allow the independent peer-level facilities to be executed on respective processors. This is generally illustrated in Fig. 10 by the inclusion of the functions A' and B' representing the messaging kernel layers of two peer-level facilities. A function call 302 from the routine A is made to the messaging kernel A' . Although A' does not implement the specific function called, a stub routine is provided to allow the messaging kernel layer A' to implicitly identify function requested by the routine A and to receive any associated function call data; the data being needed by the routine B to actually carry out the requested function. The messaging kernel layer A' prepares a message containing the call data and sends a message descriptor 306 to the appropriate messaging kernel layer B' . Assuming that the message is initiating a new communication transaction, the messaging kernel layer B' copies the message to its own shared memory. Based on the mesεage type, the messaging kernel B' identifies the specific function routine B that needs to be called. Utilizing one of its own stub routines, a call containing the data transferred by the message is then made to the routine B. When routine B returns to the stub process from which it was called, the messaging kernel layer B' will prepare an appropriate reply mesεage to the messaging kernel layer A' . The routine B return may reference data, such as the status of the returning function, that must also be transferred to the messaging kernel layer A' . This data is copied into the message before the message is copied back to the shared memory space of the A' peer- level processor. The message copy is made to the shared memory location where the original message was stored on the A' peer-level processor. Thus, the image of the original message is logically updated, yet without requiring interaction between the two messaging kernel layers to identify a destination storage location for the reply message. A "reply" message descriptor pointing to the message is then sent to the messaging kernel layer A' . The messaging kernel layer A' , upon successive evaluation of the message descriptor and the message type field of the message, is able to identify the particular process that resulted in the reply message now received. That is, the process ID as provided in the original message sent and now returned in the reply message, is read. The messaging kernel layer A' is therefore able to return with any applicable reply message data to the calling routine A in the relevant process context. A more robust illustration of the relation between two messaging kernel layers is provided in Fig. 11. A first messaging kernel layer 310 may, for example, represent the messaging kernel layer 178 of the network communications peer-level facility 162. In such case, the series of stub routines Al-X include a complete NFS stack interface as well as an interface to every other function of the network communications facility that either can directly call or be called by the messaging kernel layer 178. Consequently, each call to the messaging kernel layer is uniquely identifiable, both in type of function requested as well as the context of the process that makes the call. Where the messaging kernel layer calls a function implemented by the NFS stack of its network communications facility, a process is allocated to allow the call to operate in a unique context. Thus, the call to or by a stub routine is identifiable by the process ID, PID, of the calling or responding process, respectively. The calling process to any of the stub routines Al-X, upon making the call, begins executing in the messaging kernel layer. This execution services the call by receiving the function call data and preparing a corresponding mesεage. This is shown, for purposes of illustrating the logical process, as handled by the logical call format bubbles Al-X. A message buffer is allocated and attached to a message queue. Depending on the particular stub routine called, the contents of the mesεage may contain different data defined by different εpecific meεεage data structures. That is, each message is formatted by the appropriate call format bubble Al-X, using the function call data and the PID of the calling process. The message is then logically passed to an A message state machine for sending. The A message state machine initiates a message transfer by first isεuing a message descriptor identifying the location of the message and indicating, for example, that it is a new mesεage being εent. The deεtination of the message descriptor is the shared memory address of the message descriptor FIFO as present on the intended destination peer-level processor. The specific message descriptor FIFO is effectively selected based on the stub routine called and the data provided with the call. That is, for example, the mesεaging kernel layer 178 correlates the FSID provided with the call to the particular file system facility 164 that has mounted that particular file system. If the messaging kernel layer 178 is unable to correlate a FSID with a file system facility 164, as a consequence of a failure to export or mount the file system, the NFS request is returned to the client with an error. Once the message descriptor is pasεed to the meεsaging kernel layer 312 of an appropriate peer-level facility, the multi-tasking kernel of the messaging kernel layer 310 blocks the sending process until a reply mesεage has been received. Meanwhile, the multi-tasking of the layer 310 kernel continues to handle incoming messages, initiated by reading mesεage descriptors from its descriptor FIFO, and requests for messages to be sent based on calls received through the stub routines Al-X. The messaging kernel layer 312 is similar to the mesεaging kernel layer 310, though the implementation of the layer specifically with regard to its call format, return format, and stub routines Bl-X differ from their A layer counterparts. Where, for example, the mesεaging kernel layer 312 iε the meεsaging kernel layer 180 of the file syεtem facility 164, the εtub routines Bl-X match the functions of the UFS 182 and device driver 188 that may be directly called in responεe to a message from another facility or that may receive a function call intended for another facility. Accordingly, the preparation and handling of messages, as represented by the B message parser, call format and return format bubbles, will be tailored to the file system facility. Beyond this difference, the messaging kernel layers 310, 312 are identical. The B message state machine implemented by the multi-tasking kernel of the messaging kernel layer 312 receives a message descriptor as a consequence of the peer-level processor reading the message descriptor from its mesεage deεcriptor FIFO. Where the message descriptor is initiating a new message transaction, i.e., the mesεage modifier is zero or two, the B message state machine undertakes to copy the message pointed to by the message descriptor into a newly allocated message buffer in the local shared memory of its peer-level processor. If the mesεage modifier indicates that the message is a reply to an existing mesεage transaction, then the B message state machine assumes that the message has already been copied to the previously allocated buffer identified by the message descriptor. Finally, if the message descriptor modifier indicates that the mesεage pointed to by the mesεage is to be freed, the B message state machine returns it to the B multi-tasking kernel's free message buffer pool. Received messages are initially examined to determine their message type. This step is illustrated by the B message parser bubble. Based on message type, a corresponding data structure is selected by which the mesεage can be properly read. The process ID of the relevant servicing destination procesε is also read from the message and a context switch is made. The detailed reading of the message is illustrated as a series of return format bubbles Bl-X. Upon reading the message, the messaging kernel layer 312 selects a stub routine, appropriate to carry out the function requested by the received message and performs a function call through the stub routine. Also, in making the function call, the data contained by the message is formatted aε appropriate for tranεfer to the called routine. 3. IFC Communication Tranεactions Figure 12 illustrateε an exemplary εerieε of communication transactions that are used for a network communications facility or a local host facility to obtain known data from the disk array 24 of the present invention. Similar serieε of communication tranεactionε are used to read directory and other disk management data from the disk array. For clarity, the transfer of messages are referenced to time, though time is not to scale. Also for purposeε of clarity, a pseudo-representation of the message structures is referenced in describing the various aspects of preparing messages. a. LFS Read Transaction At a time t_, an NFS read request is received by the mesεaging kernel layer 178 of the network communications facility 162 from an executing (sending) process (PID=A$$). Alternately, the read request at t could be from a host procesε issuing an equivalent LFS read request. In either case, a corresponding LFS m e s s a g e ( m e s s a g e # l ) i s p r e p a r e d (message#l.msg_type=fc_read; meεsagetl . sender_pid=A$$; meεεage# l.dest_pid=B$$) • The destination process (PID=B$$) is known to the messaging kernel layer 178 or 194 as the "manager" process of the file system facility that has mounted the file system identified by the FSID provided with the read request. The asεociation of an FSID with a particular FS facility's PID is a product of the initialization of all of the messaging kernel layers. In general, at least one "manager" procesε iε created during initialization of each messaging kernel layer. These "manager" processes, directly or indirectly, register with a "name server manager" process (SC_NAME_SERVER) running on the host facility. Subsequently, other "manager" procesεeε can query the "name server manager" to obtain the PID of another "manager" process. For indirect relations, the supervising "manager" process, itself registered with the "name server manager" process, can be queried for the PIDs of the "manager" processes that it superviseε. For example, a single named "file system administrator" (FC_VICE_PRES) process iε utilized to supervise the potentially multiple FS facilities in the system 160. The FC_VICE_PRES process iε regiεtered directly with the "name server manager" (SC_NAME_SERVER) process. The "manager" processes of the respective FS facilities register with the "file system administrator" (FC_VICE_PRES) process — and thus are indirectly known to the "name server manager" (SC_NAME_SERVER) . The individual FS "manager" processes register with the given FSIDs of their mounted file systems. Thus, the "name server manager" (SC_NAME_SERVER) can be queried by an NC facility for the PID of the named "file εyεtem adminiεtrator" (FC_VICE_PRES) . The NC facility can then query for the PID of the unnamed "manager" process that controls access to the file system identified by a FSID. The function of a non-supervising "manager" process is to be the known destination of a message. Thus, such a "manager" process initially handles the messages received in a communication transaction. Each message is assigned to an appropriate local worker process for handling. Consequently, the various facilities need know only the PID of the "manager" process of another facility, not the PID of the worker procesε, in order to εend a request mesεage. At t_, a corresponding mesεage descriptor (md#lvme_addr; mod=0), shown as a dashed arrow, is sent to the FS's messaging kernel layer 180. At t. , the FS messaging kernel layer 180 copies down the message (message^1) , shown as a solid arrow. for evaluation, allocates a worker process to handle the request and, in the context of the worker process, calls the requested function of its UFS 182. If the required data iε already present in the memory resource 18', no communication transaction with the S messaging kernel layer 186 is required, and the FS messaging kernel layer 180 continues immediately at - Λ A - However, if a disk read iε required, the messaging kernel layer 180 is directed by the UFS 182 to initiate another communications transaction to request retrieval of the data by the storage facility 166. That is, the UFS 182 calls a storage device driver stub routine of the messaging kernel layer 180. A message (mesεage#2), including a vector address referencing a buffer location in the memory resource 18 ' (mesεage#2.mεg_type=εp_read; meεεage#2.vme_addr=xxxxh; message#2. sender_j?id=B$$; message#2.dest_pid=C$$) , is prepared. At t,., a corresponding message descriptor is εent (md#2vme_addr; mod=0) to the S meεεaging kernel layer 186. At t β , the S meεsaging kernel layer 186 copies down the message (message#2) for evaluation, allocates a worker process to handle the request and calls the requested function of its device driver 188 in the context of the worker process. Between t_ and t. , the requested data is transferred to the message specified location (message#2.vme_addr=xxxxh) in the memory resource 18'. When complete, the device driver returns to the calling stub routine of the S messaging kernel layer 186 with, for example, the εucceεεful (err=0) or unsuccessful (err=-l) status of the data transfer. Where there is an error, the message is updated (message#2.err=-l) and, at t..-, copied up to the messaging kernel layer 180 (md#2vme_addr) . A reply message descriptor (md#2vme_addr; mod=l) is then sent at t- 3 to the FC messaging kernel layer 180. However, where there is no error, a k_null_reply(msg) is used. This results in no copy of the unmodified message at t. 2 , but rather just the sending of the reply mesεage descriptor (md#2vme__addr; mod=l) at t 1 _. Upon proceεsing the message descriptor and reply message (message#2), the FS messaging kernel layer 180 unblocks and returns to the calling process of the UFS 182 (message#2.sender_pid=B$$) . After completing any processing that may be required, including any additional communication transactions with the storage facility that might be required to support or complete the data transfer, the UFS 182 returns to the stub routine that earlier called the UFS 182. The message is updated with status and the data location in the memory resource 18' (messageft1. err=0; message #2.vme_addr=xxxxh=message#l .vme_addr=xxxxh) and, at -65- t.., copied up to the messaging kernel layer 178 or 194 (md# 1vme_addr) . A reply message descriptor (md#lvme_addr; mod=l) iε then sent at t._ to the messaging kernel layer of the NC or local host, as appropriate. The messaging kernel layer 178 or 196 processes the reply mesεage descriptor and associated message. As indicated between t. fi and t ιq , the messaging kernel layer 178 or 196, in the context of the requesting procesε (PID=A$$), iε responsible for copying the requested data from the memory resource 18' into itε peer-level processor's local shared memory. Once completed, the messaging kernel layer 178 or 196 prepares a final message (message#3) to conclude its series of communication transactions with the FS messaging kernel layer 180. This message is the same as the first message (message#3=meεsage#l) , though updated by the FS facility as to mesεage type (mesεage#3.msg_type=fc_read_release) to notify the FC facility that it no longer requires the requested data space (message#3.vme_addr=xxxxh) to be held. In this manner, the FC facility can maintain its expedient, centralized control over the memory resource 18'. A c o r r e s p o nd i ng m e s s a g e d e s c r i p t o r (md#3vme_addr=md#lvme_addr; mod=0) is sent at t«_. At t_ . , the release message (message#3) is copied down by the FC messaging kernel layer 180, and the appropriate disk buffer management function of the UFS 182 is called, within the context of a worker process o f t h e r e l e vant mana ge r p r o c e s s (mesεage#3.deεt_pid=B$$) , to release the buffer memory ( essage!3.vme_addr=xxxxh) . Upon completion of the UFS memory management routine, the relevant worker process returns to the ε ub routine of the FS meεεaging kernel layer 180. The worker process and the message (message#3) are deallocated with respect to the FS facility and a reply mesεage deεcriptor (md#3vme_addr; mod=l) is returned to the messaging kernel layer 178 or 196, whichever is appropriate. Finally, at ? _, the messaging kernel layer 178 or 196 returns, within the context of the relevant process (PID=A$$) , to its calling routine. With this return, the addresε of the retrieved data within the local εhared memory is provided. Thus, the relevant procesε is able to immediately access the data as it requires. b. LFS Write Transaction Figure 13 illustrates an exemplary serieε of communication transactions used to implement an LFS write to disk. Beginning at a time t., an LFS write request is received by the mesεaging kernel layer 178 of the network communications facility 162 from an executing process (PID=A$$) in response to an NFS write request. Alternately, the LFS write request at t. could be from a host process. In either case, a corresponding m e s s a g e ( me s ε a g e ft l ) i ε p r ep a r e d (message^1.msg_type=fc_write; messaged1.sender_pid=A$$; messageft1.deεt_pid=B$$) and, at t 2 , its message descriptor (md#lvme_addr; mod=0) is sent to the FC messaging kernel layer 180. At t,, the FC messaging kernel layer 180 copies down the mesεage (message#l) for evaluation, allocateε a worker process to handle the request by the manager process (PID=B$$) , which calls the requested function of its UFS 182. This UFS function allocates a disk buffer in the memory resource 18' and returns a vector address (vme_addr=xxxxh) referencing the buffer to the FC messaging kernel layer 180. The message is again updated (message#2.vme_addr=xxxxh) and copied back to the messaging kernel layer 178 or 194 (md#lvme_addr) . A reply message descriptor (md#lvme_addr; mod=l) is then sent back to the messaging kernel layer 178 or 194, at t_. Between t fi and t q , the relevant process (PID=A$$) of the NC or host facility copies data to the memory resource 18'. When completed, the mesεaging kernel layer 178 or 194 iε again called, at t„, to complete the write requeεt. A new message (mesεage#.2=message#l) is prepared, though updated with the amount of data transferred to the memory resource 18' and mesεage type (message#2msg_type=fc_write_release) , thereby implying that the FS facility will have control over the diεpoεition of the data. Preferable, thiε meεεage utilizeε the available meεεage buffer of mesεageftl, thereby obviating the need to allocate a new message buffer or to copy data from meεεageftl. The meεsage descriptor (md#2vme_addr=md#lvme_addr; mod=0) for this mesεage iε εent at t 1f .. The meεεage iε copied down by the FC messaging kernel layer 180 and provided to a worker procesε by the relevant manager proceεε (message#2.deεt_pid=B$$) . While a reply meεεage descriptor might be provided back to the mesεaging kernel layer 178 or 194 immediately, at "t 12 , thereby releaεing the local shared memory buffer, the present invention adopts the data coherency strategy of NFS by requiring the data to be written to disk before acknowledgment. Thus, upon copying down the message at t..., the messaging kernel layer 180 calls the UFS 182 to write the data to the disk array 24'. The UFS 182, within the context of the relevant worker process, calls the messaging kernel layer 180 to initiate another communication transaction to request a write out of the data by the storage facility 166. Thus, a storage device driver stub routine of the messaging kernel layer 180 is called. A meεεage (mesεage#3), including the shared memory addresε of a buffer location in the memory reεource 18' ( m e ε s a g e # 3 . m s g _ t y p e = ε p _ w r i t e ; message#2.vme_addr=xxxxh; meεsage#2.sender__pid=B$$; message#2.dest_pid=C$$) , is prepared. At t. fi , a corresponding message descriptor is sent (md#3vme_addr; mod=0) to the S mesεaging kernel layer 186. At t._, the S meεsaging kernel layer 186 copies down the mesεage (meεsage#3) for evaluation, allocates a worker process to handle the request by the manager process (PID=C$$), which calls the requested function of its device driver 188. Between t 1o D and t__, the requested data is transferred from the message specified location (mesεage#3.vme_addr=xxxxh) of the memory reεource 18'. When complete, the device driver returnε to the calling stub routine of the S messaging kernel layer 186 with, for example, the statuε of the data transfer (err=0). The message iε updated (message#3.err=0) and, at - * * > r> . copied up to the meεεaging kernel layer 180 (md#3vme_addr) . A reply meεεage descriptor (md#3vme_addr; mod=l) is then sent at t_ 4 to the FC messaging kernel layer 180. Upon proceεεing the message descriptor and reply mesεage (mesεage#3), the FC meεεaging kernel layer 180 returnε to the calling proσeεε of the UFS 182 (message#3.εender_pid=B$$) . After completing any UFS processing that may be required, including any additional communication transactions with the storage facility that might be required to support or complete the data transfer, the UFS 182 returnε to the meεεaging kernel layer 180. At this point, the UFS 182 has completed its memory management of the memory resource 18'. At t ?t -, the messaging kernel layer 180 sendε the reply meεεage descriptor (md#2vme_addr; mod=l) to the messaging kernel layer 178 or 196, as appropriate, to indicate that the data has been transferred to the disk array resource 24'. Finally, at 2β , the mesεaging kernel layer 178 or 196 returns, within the context of the relevant worker process, to its calling routine. c. NC/Local Host Transfer Transaction Figure 14 illustrates the communication transaction and delivery of data, as provided from a NC facility process (PID=A$$) , to an application program executing in the application program layer of the local host facility. The packet, for example, could contain new routing information to be added to the route data baεe. However, εince the NC facility does not perform any significant interpretation of non-NFS packets beyond identification as an IP packet, the packet is passed to the local host facility. The local host, upon recognizing the nature of the non-NFS packet, will pass it ultimately to the IP client, aε identified by the packet, for interpretation. In this example, the IP client would be the "route" daemon. Thus, the transaction begins at t 2 , with the NC messaging kernel layer 178 writing a message descriptor (md#l.vme_addr; mod=0) to the host messaging kernel layer 194. The referenced message ( m es sage# l . msg_typ e = nc_rec v_ip_p kt ; message#l.εender_pid=D$$; message^l.deεt_pid=E$$) is copied down, at t.,, by the host messaging kernel layer 194. A reply message descriptor (md#1.vme_addr; mod=3) is then returned to the NC messaging kernel layer 178 The packet is then passed, by the local host mesεaging kernel layer 194, to the TCP/UDP layers 204 of the local host facility for processing and, eventually, delivery to the appropriate application program. As shown at t... the application program may subsequently call the host messaging kernel layer 194, either directly or indirectly through the system call layer. Thiε call could be, for example, iεεued as a consequence of the application program making a εyεtem call layer call to update the hoεt's IP route database. As described earlier, this call has been modified to also call the host mesεaging kernel layer 194 to send a mesεage to the NC facility to εimilarly update itε IP route databaεe. Thus, a meεεage descriptor (md#2.vme_addr; mod=0) iε εent at t.,. to the NC messaging kernel layer 178. The referenced message ( m e s s a g e # 2 . m s g_typ e = n c_a dd_r o u t e ; meεsage#2.sender_pid=E$$; meεsage#l.deεt_pid=D$$) is copied up, at t. fi , by the NC messaging kernel layer 178. The NC messaging kernel layer 178 then calls the NC facility function to update the IP route database. Finally, a reply mesεage descriptor (md#2.vme_addr; mod=l) is returned to the local host messaging kernel layer 194 at t.-. d. NC/NC Route Transfer Transaction Figure 15 illustrateε the routing, or bridging, of a data packet two NC facility processes. The two NC processes may be executing on separate peer-level processors, or exist as two parallel processes executing within the same NC facility. The packet, for example, is intercepted at the IP layer within the context of the first process (PID=A$$). The IP layer identifieε the logical NC facility that the packet is to be routed to calls the mesεaging kernel layer 178 to prepare an appropriate meεεage (meεεage#l). The data packet itself is copied to a portion of the memory resource 18' (vme_addr=xxxxh) that is reserved for the specific NC facility; this memory is not under the control of any FS facility. Thus, at t_ , the NC messaging kernel layer 178 writes a message descriptor (md#1.vme_addr; mod=0) to the second messaging kernel layer 178. The referenced mesεage (meεεage#l. mεg_type=nc_forward_ip_pkt; messages 1. sender_pid=F$$; messages1 • eεt_pid=G$$; m e ε ε a g e S 1 • v m e _ a d d r = x x x x h ; message l.ethernet_dst_net=xx) is copied down, at t- , by the second NC mesεaging kernel layer 178. The data packet iε then copied, between t. and t„ from the memory reεource 18' to the local εhared memory of the second NC peer-level processor. Since the first NC facility must manage itε portion of the memory reεource 18', the εecond NC meεsaging kernel layer 178, at t q , returns a reply mesεage deεcriptor (md 1.vme_addr; mod=l) back to the first NC messaging kernel layer 178 at t q . This notifies the first NC facility that it no longer requires the memory resource 18' data space (meεεage 1 •vme_addr=xxxxh) to be held. In this manner, the first NC facility can maintain expedient, centralized control over its portion of the memory resource 18' . The packet data is then pasεed, by the εecond NC meεεaging kernel layer 178, to the IP layer of itε NC facility for procesεing. 4. Detailed Communication Transaction Messages. Syntax, and Semantics A Notation for Communication Transactions A terse notation for use in deεcribing communication transactions has been developed. This notation does not directly represent the code that implements the tranεactions, but rather is utilized to describe them. A example and explanation of the notation is made in reference to a LFS type tranεaction requeεting the attributeε of a given file. The communication tranεaction: fc_get_attributes( FILE,ATTRIBUTES ); identifies that a message with type FC_GET_ATTRIBUTES, the expected format of the mesεage, when εent to the FS facility, for example, is a typedef FILE, and that when the message is returned, its format is a typedef ATTRIBUTES. A second convention makes it very clear when the FS facility, for example, returns the message in the same format that it was originally sent. The communication transaction: get_buffer( BUFFER,***); describes a transaction in which the NC facility, for example, sends a typedef BUFFER, and that the message iε returned uεing the εame εtructure. If a facility can indicate εucceεε by returning the message unchanged (k__null_reply() ) , then the format is: free_buffer( BUFFER,* ); Sometimeε, when facilities use standard structures, only some of the fields will actually have meaning. The following notation identifies meaningful fields: get_buffer( BUFFER{data_len} , ***{ ata_le ,data_ptr} ) ; This transaction notation describeε the same transaction as get_buffer above, but in more detail. The facility requests a buffer of a particular length, and the responding facility returns a pointer to the buffer along with the buffer's actual length. a. FS Facility Communication Transactions The communication transactions that the FS facilities of the present invention recognizes, and that the other facilities of the present invention messaging kernel layer recognize as appropriate to interact with the FS facility, are summarized in Table 4 below. Table 4 Summary of FS Communication Transactions LFS Configuration Management fc_find_manager (FC_MOUNT_T, ***{errno,fc_pid} ) fc_mount (FC_MOUNT_T, ***{errno,fc_pid,file} ) fc_unmount (FC_STD_ {partition.fsid} ,* {errno} ) LFS Data Transfer Messages fc_read ( FC_RDWR_T{un.in} , ***{errno,un.out. {bd,vattr} } ) fc_write ( FC_RDWR_T{un.in} , *** {errno,un.out. {bd,vattr} } ) fc_readdir ( FC_RDWR_T{un.in} , *** {errno,un.out. {bd,new_offset} } fc_readlink ( FC_RDWR_T{un. in.file,un. in.cred} , ***{errno,un.out.bd} ) fc release ( FC RDWR T{un.out.bd} ,* {errno} ) LFS File Management Messages fσ_null K_MSG,***) fσ_null_nul1 K_MSG, *) fc_getattr FC_STD_T{cred,file,un.mask} , FC_FILE_T{errno,vattr} ) fc_εetattr FC SATTR T, FC FILE T{errno,vattr} fc_lookup FC_DIROP_T{cred,where} , FC FILE T fc_create FC_CREATE_T, FC_FILE_T fc_remove FC_DIROP_T{cred,where} , *{errno} ) fc_rename FC_RENAME_ , *{errno} fc_link FC_LINK_T, *{errno} ) fc_εymlink FC_SYMLINK_T, * {errno} ) fc_rmdir FC_DIR0P_T{cred,where} , *{errno} ) fc εtatfs FC STATFS T{fsid},***) VOP. VFS and Other Miscellaneous LFS Messages fc_fsync ( FC_STD_T{cred,file} , *{errno} ) fc_accesε ( FC_STD_ {cred,file,mode} , *{errno} ) fc_syncfs ( FC_STD_T{cred,fεidj , *{errno} ) The uεe of these communication transactions are best illustrated from the perspective of their use. An FS facility process named FC_VICE_PRES directs the configuration of all FS facilities in the system 160. Even with multiple instantiations of the FS facility, there is only one FC_VTCE_PRES procesε. There are also one or more unnamed manager processes which actually handle most requeεts. Each file εystem- -or disk partition—in the system 160 belongs to a particular manager; however, a manager may own more than one file εyεtem. Since managerε are unnamed, would-be clients of a file system first check with FC_VICE_PRES to get the FS facility pid of the appropriate manager. Thus, the FC_VICE_PRES process does no actual work. Rather, it simply operates to direct requests to the appropriate manager. To provide continuous service, managers must avoid blocking. Managerε farm out requeεtε that would block to a pool of unnamed file controller worker processes. These details are not visible to FS facility clientε. The εignificant meεεage εtructureε uεed by the FS facility are given below. For clarity, the commonly used structureε are described here. An FSID (file system identifier) identifies an individual file system. An FSID is simply the UNIX device number for the disk array partition which the file syεtem lives on. An FC_FH structure (file controller file handle) identifies individual files. It includes an FSID to identify which file syεtem the file belongs to, along with an inode number and an inode generation to identify the file itself. Start-up. Mounting and Unmounting Once the FC peer-level processor has booted an instantiation of the FS facility, the first FS facility to boot spawns an FC_VICE_PRES procesε which, in turn, createε any managers it requires, then waits for requests. Besides a few "internal" requests to coordinate the mounting and unmounting of files syεtems is the operation of multiple file system facilities, The only requeεt it acceptε is: fc_find_manager ( FC_MOUNT__T,***{errno,fc_pid} ) ; The input message includes nothing but an FSID identifying the file system of interest. The successful return value is an FS facility process id which identifies the manager responεible for this file system. Having found the manager, a client facility with the appropriate permissions can request that a file syεtem be made available for user requeεts (mount) or unavailable for user requests (unmount) . These requests are made by the local host facility, through its VFS/LFS client interface; requests for the mounting and unmounting of file systems are not received directly from client NC facilities. The transaction: fc_mount ( FC_MOUNT_ , ***{errno,fc_pid,file} ); returns the root file handle in the requested file system. The unmount transaction: fc_unmount ( FC_STD_T{fsid} , *{errno} ); returnε an error code. (The * in the tranεaction deεcription indicateε that a k_null_reply( ) is possible, thus the caller must set errno to zero to detect a εucceεεful reply.) Data Transfer Messages There are four common requests that require the transfer data. These are FC_READ, FC_READDIR, FC_READLINK, and FC_WRITE. The FS facility handles these requests with a two message protocol. All four transactions are similar, and all use the FC_RDWR_T mesεage εtructure for their messages. typedef struct { void *buf; /* Buffer id. Valid if non-NULL. */ vme__t addr; /* Pointer to data. */ int count; /* Length of data. */ } FC_BUF_DESC; Sdefine FC RDWR BUFS 2 typedef struct { int type; int errno; union { struct { FC_CRED cred; /* credentials */ int flags; FC_FH file; int offset; int count; } in; struct { /* * Structure used in responεe to * fc_release mesεage. */ FC_BUF_DESC bd[FC_RDWR_BUFS] ; /* Buffer deεcriptors. */ FC_VATTR vattr; } out; } un; } FC_RDWR_T; The FC_READ tranεaction iε described in some detail. The three by other transactions are described by comparison. A read data communication transactionε iε: fc_read ( FC__RDWR_T{un.in} , ***{errno,un.out. {bd,vattr} } ); As sent by a client facility, the "in" structure of the union is valid. It specifies a file, an offset and a count. The FS facility lockε the buffers which contain that information; a series of message transactions with the S facility may be necessary to read the file from disk. In its reply, the FS facility uses the "out" structure to return both the attributes of the file and an array of buffer descriptors that identify the VME memory locations holding the data. A buffer descriptor is valid only if it's "buf" field iε non-zero. The FS facility useε non-zero values to identify buffers, but to client facilities they have no meaning. The attributes and buffer descriptors are valid only if no error has occurred. For a read at the end of a file, there will be no error, but all buffer descriptors in the reply will have NULL "buf" fields. After the client facility has read the data out of the buffers, it sendε the εame message back to the FS facility a second time. This time the transaction is: fc_release ( FC_RDWR_T{un.out.bd} , *{errno} ); Thiε fc_release request must use the εame meεεage that was returned by the fc_read request. In the reply to the fc_read, the FS facility sets the mesεage "type" field of the meεεage to make thiε work. The following pεeudo-code fragment illuεtrateε the sequence: msg = ( FC_RDWR_T*)k_alloc_msg() ; initialize_meεεage; mεg - k_send( msg, fc_pid ); copy_data_from_bufferε_into_local_memory; mεg = k_εend( mεg, fc_pid ); The εame message, or an exact duplicate, must be returned because it contains the information the FS facility needs to free the buffers. Although the transaction summary of Table 4 shows just one fc_release transaction, there are really four: one for each type of data transfer: fc_read release, f c_wri te_re 1 ea ε e , f c_re add i r_re 1 e a ε e and fc_read_link_releaεe. Since the FS facility sets the "type" field for the second mesεage, thiε makes no difference to the client facility. If the original read transaction returned an error, or if none of the buffer descriptorε were valid, then the releaεe is optional. The FC_WRITE transaction is identical to FC_READ, but the client facility is expected to write to the locations identified by the buffer descriptors instead of reading from them. The FC_READDIR transaction is εimilar to read and write, but no file attributes are returned. Also, the specified offset is really a magic value—also sometimes referred to as a magic cookie--identifying directory entries instead of an absolute offset into the file. This matches the meaning of the offset in the analogous VFS/VOP and NFS versionε of readdir. The contentε of the returned buffers are "dirent" structureε, aε deεcribed in the conventional UNIX "getdents" system call manual page. The FC_READLINK transaction is the simplest of the four communication transactions. It returns no file attributes and, since links are always read in their entirety, it requires no offset or count. In all of theεe tranεactionε, the requeεted buffers are locked during the period between the first requeεt and the second. Client facilities should send the fc_release meεεage aε soon as possible, because the buffer is held locked until they do, and holding the lock could slow down other client facilities when requesting the same block. In the preferred embodiment of the present invention, the these four transactions imply conventional NFS type permisεion checking whenever they are received. Although conventional VFS/UFS calls do no permission checking, in NFS and the LFS of the present invention, they do. In addition, the FS facility messages also supports a "owner can always read" permisεion that iε required for NFS. LFS File Management Messages The LFS communication transactions, as described below, are similar to conventional NFS call functions with the same nameε. The communication tranεaction: fc_nul1 (K_MSG,***); does nothing but uses k_reply(). The communication transaction: fc_null_null( K_MSG, *) ; alεo doeε nothing, but uses the quicker k_null_reply( ) . Both of these are intended mainly as performance tools for measuring message turnaround time. The communication transaction: fc_getattr (FC_STD_T{cred,file,un.mask} , FC_FILE_T{errno,vattr} ) ; gets the vnode attributes of the specified file. The mask specifieε which attributes should be returned. A mask of FC_ATTR_ALL gets them all. The same structure is always used, but for un-requested values, the fields are undefined. The communication transaction: fc_setattr ( FC_SATTR_T,FC_FILE_T{ rrno,vattr} ); sets the attributes of the specified file. Like fc_getattr, fc_setattr uses a mask to indicate which values should be set. In addition, the special bits FC_ATTR_TOUCH_[AMC]TIME can be set to indicate that the access, modify or change time of the file should be set to the current time on the server. This allows a Unix "touch" command to work even if the times on the client and server are not well matched. The communication transaction: fc_lookup ( FC_DIROP_T{cred,where} ,FC_FILE_T ); searches a directory for a specified file name, returning the file and it's attributes if it exists. The "where" field of FC DIROP T is an FC DIROP structure which contains a file, a name pointer, and a name length. The name pointer contains the vme addresε of the name. The name may be up to 256 characters long, and must be in memory that the FS facility can read. The communication transaction: fc_create( FC_CREATE_T,FC_FILE_T ); creates files. The FC_CREATE_T deεcribes what type of file to create and where. The vtype field may be used to specify any file type including directories, so mkdir is not εupported. If the "FC_CREATE_EXCL" bit is set in the flag field, then fc_create will return an error if the file already existε. Otherwise, the old file will be removed before creating the new one. The communication transaction: fc_remove ( FC_DIROP_T{cred,where} ,*{errno} ) ; removeε the specified name from the specified directory. The communication transaction: fc_rename ( FC_RENAME_T, * ); changeε a file from one name in one directory to a different name in a (poεεibly) different directory in the εame file system. The communication transaction: fc__link ( FC_LINK_T, *{errno} ) ; links the specified file to a new name in a (posεibly) new directory. The communication tranεaction: fc_symlink ( FC_SYMLINK_T, *{errno} ); creates the specified εymlink. The communication transaction: fc_rmdir ( FC_DIROP_T{cred,where} , *{errno} ) ; removes a directory. The arguments for fc_rmdir are like those for fc_remove. The communication transaction: fc_statfs ( FC_STATFS_T{fsid} ,*** ); returnε file εyεtem εtatiεtics for the file syεtem containing the specified file. VFS/VOP LFS Support Transactions The communication transactions described below are provided to support the VFS/VOP subroutine call interface to the LFS client layer. Most VOP calls can be provided for using the meεεage already defined above. The remaining VOP function call εupport iε provide by the following transactions. The communication transactions: fc_fsync ( FC_STD_T{cred,file} ,*{errno} ); fc_syncfs ( FC_STD_T{cred,fsid} , *{errno} ); enεure that all blocks for the referenced file or file system, respectively, are flushed. The communication transaction: fc_access( FC_STD_T{cred,file,mode} ,* {errno} ); determines whether a given type of file access is legal for specified credentials ("cred") on the specified file. The mode value is "FC_READ_MODE" , "FC_WRITE_MODE" , or "FC_EXEC_MODE" . If the mode is legal, the returned errno is zero. Table 5 listε the inter-facility message types supported by the FS facility. Table 5 FS Facility Mesεage Typeε (K MSGTYPE) Sdefine FC_ID ( (long) ( ('F'<<8) j ('C') ) << 16 ) \* External Meεsages *\ Sdefine FC_FIND_MANAGER Sdefine FC_MOUNT Sdefine FC_UNMOUNT Sdefine FC_READ Sdefine FC_WRITE Sdefine FC_READDIR Sdefine FC_READLINK Sdefine FC_READ_RELEASE Sdefine FC_WRITE_RELEASE Sdefine FC_READDIR_RELEASE Sdefine FC READLINK RELEASE Sdefine FC_ NULL Sdefine FC ~ NULL_NULL Sdefine FC~ GETATTR Sdefine FC~ SETATTR Sdefine FC_ " LOOKUP Sdefine FC ~ " CREATE Sdefine FC ~ " REMOVE Sdefine FC_ " RENAME Sdefine FC ~ " LINK Sdefine FC- " SYMLINK Sdefine FC_RMDIR ( 22 j FC_ID ) Sdefine FC_STATFS ( 23 I FC_ID ) Sdefine FC_FSYNC ( 24 j FC ID ) Sdefine FC__ACCESS ( 25 i FC_ID ) Sdefine FC_SYNCFS ( 26 i FC_ID ) /* Internal Meεεageε. */ Sdefine FC_REG_PARTITION ( 27 i FC_ID ) Sdefine FC UNREG PARTITION ( 28 ! FC_ID ) The FS facility message structureε are listed below. /* Standard Structure which handles many messageε. typedef εtruct { /* Access credentials */ /* For fc_get_server. */ /* {READ,WRITE,EXEC} for fc_access. */ /* FS facility pid of server. /* Mask attributes. (FC ATTR *) . */ /* Structure for fs control — mounting, unmounting. */ typedef struct { K_MSGTYPE type; long errno; long fc; /* IN: Which FC to use. (i.e. 0, 1, ...)*/ long flags; /* IN: Mount flags. */ FC__PARTITION partition; /* IN: Describes SP partition to use. */ K_PID fc pid; /* OUT: PID of manager for FS. */ FC_FH file; /* OUT: Root file handle of file system. */ } FC MOUNT T; typedef εtruct { K MSGTYPE type; typedef εtruct { void *buf; vme_t addr; /* fc returned data. */ long count; /* fc returned data length. */ } FC_BUF_DESC; The FC_BUF_DESC structure is used in the two message data transfer protocols. A typical sequence iε: fσ_read ( FC_RDWR_T{flags,un.in} , FC_RDWR_T{flags,un.out} ); fc_releaεe ( FC_RDWR_T{flagε,un.out} , FC_RDWR_T{flags,un.out} ) Note that the "out" union member is the output for the first mesεage and the input for the second. Sdefine FC RDWR BUFS 2 long count; /* User requested count. */ } in¬ struct { /* Structure used in response to fc_release meεεage. */ FC_BUF_DESC b [FC_RDWR_BUFS] ; /* Buffer descriptor. */ FC VATTR vattr; /* For responses. */ long new offset; /* For READDIR. */ } } un; } FC_RDWR_T; /* Sdefine FC_RDWR_SYNC 0x0001 /* Sdefine FC_RDWR_NOCACHE 0x0002 /* Don't cache buffer. */ This structure is used in those operations that take a directory file handle and a file name within that directory, namely "lookup", "remove", and "rmdir". } FC_DIR0P_T; Not all fields that can be set can be specified in a create, so inεtead of including FC_SATTR, only the values that can be set aε included. } FC_CREATE_T; /* Values for the flag. */ Sdefine FC CREATE EXCL 0x0001 /* Exclusive. */ File to create. */ File permiεεions. */ Pointer to contents r εymlink */ typedef struct { K_MSGTYPE type; long errno; FC_FSID fsid; u_long bsize; /* Block size. 7 u long blocks; /* Total number of blocks. */ u_long bfree; /* Free blocks. */ u_long bavail; /* Blocks available to non-priv users. */ u_long files; /* Total number of file slots. */ u_long ffree; /* Number of free file εlotε. */ u_long favail; /* File slotε available to non-priv users. */ struct ti eval stime; /* Server's current time of day. */ } FC_STATFS_T; Sdefine FC_MAXNAMLEN 255 Sdefine FC MAXPATHLEN 1024 struct fc_dirent { u_long d_off; /* offset of next disk directory entry */ u_long d_fileno; /* file number of entry */ u_short d_reclen; /* length of thiε record */ u_short d_namlen; /* length of εtring in d_name */ char d_name[FC_MAXNAMLEN + 1]; /* name (up to MAXNAMLEN + 1) */ }; b. NC Facility Communication Transactions The communication transactionε that the NC facilities of the present invention recognize, and that the other messaging kernel layers of the present invention messaging kernel layer recognize as appropriate to interact with the NC facility, are summarized in Table 6 below. The NC facility also uses and recognizes the FS facility communication transactions described above. Table 6 Summary of NC Communication Transactions Network Interface IQCTL Messages REGISTER_DL_T, ***{status} ) IFIOCTL_T{unit,promis} , ***{status} ) IFIOCTL_T{unit,mc_addr} , ***{εtatuε} ) IFIOCTL_T{unit,mc_addr} , ***{εtatuε} ) IFIOCTL_T{unit,flagε} , ***{εtatuε} ) IFIOCTL_T{unit} , ***{εtatuε,flags} ) IFIOCTL_T{unit,metric} , ***{statuε}) IFIOCTL_T{unit,if_addr} , ***{εtatuε} ) IFIOCTL_T{unit} , ' ***{status,if_addr} ) IFSTATS_T,*** ) IFIOCTL_T{unit,flags} , ***{status} ) nc_get__macflags ( NC:_IFIOCTL__T{unit} , ***{statuε,flagε} nσ_set_ip_braddr ( NC :_INIOCTL_T, *** ) nc_get_ip_braddr ( NC :_INIOCTL_T, *** nc_set_ip_netmaεk ( NC INIOCTL_T, *** \ nσ_get_ip_netmaεk ( NC ._INIOCTL_T, **•_. \ nc_add_arp_entry ( NC ARPIOCTL_T, *** \ nc_del_arp_entry ( NC ARPIOCTL_T, *** nc_get_arp_entry ( NC ARPIOCTL_T, *** nc_add__route ( NC :_RTIOCTL_T, *** \ nc del route ( NC RTIOCTL T, *** *• ) NFS Configuration Messages nc_nfs_start ( NC_NFS_START_ , * ) nc_nfε_export ( NC_NFS_EXPORT_T, ***{errno} ) nc_nfs_unexport ( NC_NFS_UNEXPORT_T, ***{errno} nc_nfs_getstat ( NC_NFS_STATS_T,*** ) Network Interface Data Messages nc_xmit_pkt ( NC_PKT_IO_T, * ) nc_recv_dl_pkt ( NC_PKT_IO_T, * ) ' nc_recv_ip_pkt ( NC_PKT_IO_T, * ) nc_recv_promis_pkt ( NC_PKT_IO__T, *) nc_forward_ip_pkt ( NC_PKT_IO_T, * ) Secure Authentication Messages ks_decrypt ( KS_DECRYPT_T{netname,netnamelen,desblock} , ***{rpcstatus,kεstatus,deεblock} ) ks_getcred ( KS_GETCRED_T{netname,netnamelen} , ***{rpcstatus,ksstatus,cred} ) A network communications facility can exchange messages with the host facility, file system facility and any other network communications facility within the system 160. The host facility will exchange messages with the network communications facility for configuring the network interfaces, managing the ARP table and IP routing table, and sending or receiving network packets. In addition, the host facility will exchange mesεageε with the network communications facility for configuring the NFS server stack and to respond in support of a secure authentication service request. The network communications facility will exchange mesεageε with the file system facility for file service using the external FS communication transactions discuεεed above. Finally, a network communication facility will exchange messages with other network communication facilities for IP packet routing. System Call Layer Chances The exportfs() , unexport() , ' rtrequest() , arpioctl() and in_control() function calls in the syεtem call layer have been modified. The exportfs( ) and unexport() functions are called to export new file systems and unexport an exported file system, respectively. A call to these modified functions now also initiates the appropriate NC_NFS_EXPORT or NC_NFS_UNEXPORT communication transactionε to each of the network facility. The rtrequeεtO function iε called to modify the kernel routing table. A call to the modified function now also initiates an appropriate NC communication tranεaction (NC_ADD_ROUTE for adding a new route or NC_DEL_ROUTE for deleting an existing route) to each of the network facility. The arpioctlO function is called to modify the kernel ARP table. This function has now been modified to also initiate the appropriate NC communication transaction (NC_ADD_ARP for adding a new ARP entry or NC_DEL_ARP for deleting an existing entry) to each of the network facility. Finally, the in_control() function is called to configure the Internet Protocol parameters , such as setting the IP broadcast addresε and IP network mask to be used for a given interface. This function has been modified alεo initiate the appropriate NC communications transaction (NC_SET_IP_BRADDR or NC_SET_IP_NETMASK ) to the appropriate network facility. NC Facility Initialization When a network communications facility iε initialized following bootup, the following manager processes are created: nc_nfs_vp<n> NFS server process for processing NFS_EXPORT and NFS_UNEXPORT communication transactions from the host; nc_dlctrl<n> Network interface control procesε for processing IOCTL communication transactionε from the hoεt; and nc_dlxmit<i> Network tranεmit proceεs for proceεεing NC_XMIT_PKT and NC_F WD_I P_PKT communication transactionε. where : <n> is the network processor number: 0,1,2, or 3. <i> is the network interface (LAN) number: 0,1,2,3,4,5,6, or 7. Once initialized, the NC facilities reports the "names" of these processes to a SC_NAME_SERVER manager procesε, having a known default PID, εtarted and running in the background, of the host facility. Once identified, the host facility can configure the network interfaces (each LAN connection iε εeen aε a logical and phyεical network interface) . The following command iε typically issued by the Unix start-up script for each network interface: ifconfig <interface name> <hoεt name> <options> up where: •interface name) is the logical name being used for the interface; <hoεt name) is the logical host name of the referenced <interface name). The ifconfig utility program ultimately results in two IOCTL commands being isεued to the network processor: nc_set_ifflags( flags = UP + <options> ); nc_εet_ifaddr( ifaddr=addreεs_of_hoεt- name(<hoεt name)) ); The mapping of <host name) to address is typically specified in the "/etc/hosts" file. To εtart the NFS service, the following commands are typically then issued by the Unix start-up script: nfsd <n> exportfs -a < 5 where: <n) specifies number of parallel NFS server proceεε to be εtarted. The nfεd utility program initiates an "nc_nfε_εtart" communication transaction with all network 10 communication facilities. The "exportfs" communication transaction is used to pass the list of file systems (specified in /etc/exports) to be exported by the NFS server using the "nc_nfs_export" communication transaction. 15 Once the NFS service is initialized, incoming network packets address to the "NFS server UDP port" will be delivered to the NFS server of the network communications facility. It will in turn issue the necesεary FS communication tranεactions to obtain file 20 service. If secure authentication option is used, the NFS server will isεue requeεts to the Authentication server daemon running on the host procesεor. The conventional authentication services include: mapping "* (ks_getcred( ) ) a given <network name) to Unix style 25 credential, decrypting (ks_decrypt() ) a DES key using the public key associated with the <network name) and the secret key asεociated with user ID 0 (ie. with the <network name) of the local host) . Routing Once a network communication facility is initialized properly, the IP layer of the network communication facility will perform the appropriate IP packet routing based on the local routing database table. This routing table iε managed by the hoεt facility using the "nc_add_route" and "nc_del_route" IOCTL commands. Once a route has been determined for a particular packet, the packet iε dispatched to the appropriate network interface. If a packet is destined to the other network interface on the same network communication facility, it is procesεed locally. If a packet iε destined to a network interface of another network communication facility, the packet is forwarded uεing the "nc_forward_ip_pkt ( ) " communication tranεaction. If a packet is destined to a conventional network interface attached to the host facility, it is forwarded to the host facility using the "nc_forward_ip_ kt() " communication transaction. The host facility provides the basic network front-end service for system 160. All packets that are addresεed to the system 160, but are not addressed to the NFS stack UDP server port, are forwarded to the hoεt facility'ε receive manager process using the following communication transactionε: nc_recv_dl_pkt ( NC_PKT_IO_T, * ); where the packet type iε not IP; and nc_recv_ip_pkt ( NC_PKT_IO_T, * ); where the packet type iε IP. The communication tranεaction: nc_recv_promis_pkt ( NC_PKT_I0_T, *) ,- transfers packets not addressed to εyεtem 160 to the hoεt facility when a network communication facility has been configured to receive in promiscuous mode by the host facility. To transmit a packet, the host facility initiates a communication transaction: nc_xmit_pkt ( NC_PKT_IO_T, *) ; to the appropriate network communication facility. Finally, the host facility may monitor the messageε being handled by a network communication facility by issuing the communication transaction: nc_recv_promiε_pkt ( NC_PKT__IO_T, *) ; to the appropriate network communication facility. Table 7 lists the inter-facility message types supported by the FS facility. Table 7 NC Facility Message Types Sdefine NC_ID ( (long) ( ('N'<<8) { CO ) << 16 ) Sdefine NC_IOCTL_CMD_CLASS(type) (type & OxfffffffO) /* NC "mac" ioctl's */ ((1 '<< 4) + NC_ID) (MAC_IOCTL_CMDS+0) (MAC_IOCTL_CMDS+1) (MAC_IOCTL_CMDS+2) (MAC IOCTL CMDS+3) ((2 << 4) + NC_ID) (DL IOCTL CMDS+0) (DL _ IOCTL "" CMDS+1) (DL~ IOCTL " CMDS+2) (DL ~ IOCTL CMDS+3) (DL ~ IOCTL " CMDS+4) (DL~ ' lOCTL ~ CMDS+5) (DL ~' lOCTL " CMDS+6) (DL~ " lOCTL ~ CMDS+7) ((3 << 4) + NC_ID) (IN_IOCTL_CMDS+0) (IN_IOCTL_CMDS+1) (IN_IOCTL_CMDS+2) (IN IOCTL CMDS+3) ((4 << 4) + NC_ID) (ARP_IOCTL_CMDS+0) (ARP_IOCTL_CMDS+1) (ARP IOCTL CMDS+2) ((5 << 4) + NC_ID) (RT_IOCTL_CMDS+0) (RT_IOCTL__CMDS+1) ; ation transactions. */ ((6 << 4) + NC_ID) (NC_DLXMIT_MSGTYPES+0) (NC_DLXMIT_MSGTYPES+1) /* Data communication transactions to host receiver processes. */ Sdefine NC_DLRECV_MSGTYPES ((7 << 4) + NC_ID) Sdefine NC_RECV_DL_PKT (NC DLRECV_MSGTYPES+0) Sdefine NC_RECV_PROMIS_PKT (NC ~ DLRECV_MSGTYPES+1) Sdefine NC RECV IP PKT (NC " DLRECV MSGTYPES+2) /* NFS server communication transactions */ Sdefine NFS_CMDS ((8 << 4) + NC_ID) Sdefine NC_NFS_START (NFS_CMDS+0) Sdefine NC l _NFS_EXPORT (NFS_CMDS+1) Sdefine NC_NFS_UNEXPORT (NFS_CMDS+2) Sdefine NC_NFS_GETSTAT (NFS_CMDS+3) Sdefine NC NFS STOP (NFS CMDS+4) The NC facility message structures are listed below. /' * exported vfs flags. */ Sdefine EX_RDONLY 0x01 /* exported read only */ Sdefine EX_RDMOSTLY 0x02 /* exported read mostly */ Sdefine EXMAXADDRS 10 /* max number address list */ typedef struct { u_long naddrs; /* number of addresses */ vme_t addrvec; /* pointer to array of addresses */ } NC EXADDRLIST; /* * Associated with AUTH_UNIX is an array of internet * addresεeε to check root permiεεion. */ Sdefine EXMAXROOTADDRS 10 typedef εtruct { NC_EXADDRLIST rootaddrs; } NC JNIXEXPORT; /* * Associated with AUTH_DES is a list Of network names * to check root permission, plus a time window to * check for expired credentials. */ Sdefine EXMAXROOTNAMES 10 typedef struct { u_long nnames; vme_t rootnames; /* names that point to netnames */ vme_t rootnamelens; /* lengths */ u_int window; } NC_DESEXPORT; typedef struct { long val[2]; /* file syεtem id type */ } fsid_t; /* File identifier. Should be unique per filesyεtem on a εingle machine. */ Sdefine MAXFIDSZ 16 εtruct fid { u_εhort fid_len; /* length of data in bytes */ char fid_data[MAXFIDSZ] ; /* data */ }; ***************************************************** * NFS Server Communication transaction Structures. **************************************************** / typedef struct { K_MSGTYPE m_type; int nservers; /* number of servers to start up */ } NC NFS START T; typedef struct { K_MSGTYPE m_type; long errno; /* error returned */ fsid_t fεid; /* FSID for directory being exported */ εtruct fid fid; /* FID for directory being exported */ long flags; /* flags */ u_εhort anon; /* uid for unauthenticated requeεtε */ long auth; /* switch for authentication type */ union { NC JNIXEXPORT exunix; /* case AUTH_UNIX */ NC_DESEXPORT exdes; /* case AUTH_DES */ } un; NC_EXADDRLIST writeaddrs; } NC NFS EXPORT T; typedef struct { K_MSGTYPE m_type; long errno; /* error returned */ fsid_t fεid; /* of directory being unexported */ εtruct fid fid; /* FID for directory being unexported */ } NC NFS UNEXPORT T; /' * Return server statistics */ total RPC calls */ bad RPC calls */ total NFS calls */ lls that failed */ lls for each request } NC NFS STATS T; * Network Interface IOCTL communication tranεaction εtructureε typedef εtruct { K_MSGTYPE m_type; short status; /* output */ char unit; /* Only used with IF, MAC and IN commands. */ char , pad; K_PID receiver_pid; short mem_xfer_mode; /* 0-normal, 1-VME block, 2-AEP */ long recv_mem_size; /* I */ long recv__mem_start_addr;/* I */ ETHADDR intf_addr; /* O: address of interface */ } NC REGISTER DL T; typedef struct { K_MSGTYPE m_type; short statuε; /* output */ char unit; /* Only used with IF, MAC and IN commands. */ char pad; union { long promis; /* I */ ETHADDR mc_addr; /* I: add and delete */ short flagε; /* I: εet flag; O: get flag */ long metric; /* ~ */ εtruct εockaddr if_addr; /* } un; NC IFIOCTL T; typedef εtruct { K_MSGTYPE m_type; εhort εtatuε; /* output */ char unit; /* Only uεed with IF, MAC and IN commands. */ char pad; struct if_statε { long if_ipackets; /* packets received */ long if_ibyteε; /* bytes received */ long if_ierrors; /* input errors */ long if_opackets; /* packets sent */ long if_obytes; /* bytes sent */ long if_oerrors; /* output errors */ long if_collisions; /* CSMA collisions */ } if_stats; } NC IFSTATS T; typedef struct { K_MSGTYPE m_type; short statuε; /* output */ char unit; /* Only uεed with IF, MAC and IN commands. */ char pad; union { struct in_addr br_addr; /* */ struct in addr net mask; /* */ } un; } NC INIOCTL T; typedef struct { K__MSGTYPE m_type; short status; /* output */ char unit; /* Only used with IF, MAC and IN commands char pad; struct arpreq arp_req; } NC ARPIOCTL T; typedef struct { K_MSGTYPE m_type; short status; /* output */ char unit; /* Only uεed with IF, MAC and IN commandε. */ char pad; εtruct rtentry route_req; } NC RTIOCTL T; /' * Network Interface Data Communication transaction Structure typedef εtruct { long len; caddr_t address; } PKT DATA BUFFER; Sdefine MAX_DL_BUFFRAG 4 Sdefine VME_XFER_MODE_NORMAL 0 Sdefine VME_XFER_BLOCK 1 Sdefine VME XFER AEP 2 /* enhanced protocol */ typedef εtruct ether_xmit { K_MSGTYPE m_type; char εrc_net; /* Source of packet. */ char dst_net; /* Destination of packet. */ char vme_xfer_mode; /* What transfer mode can be used to access data in buflist. */ char padl; short pktlen; /* Total packet length. */ short pad2; PKT_DATA_BUFFER pkt_buflist[MAX_DL_BUFFRAG+1] ; } NC PKT IO T; ***************************************************** * Secure Authentication Server Communication transactions ****************************************************/ /* * Name under which the key server registerε. */ Sdefine KEYSERV NAME "KEYSERV" /* Key server meεεage typeε. */ Sdefine KS_DECRYPT 69 Sdefine KS GETCRED 137 typedef εtruct { K_MSGTYPE type; u_long rpcstatus; /* RPC status */ u_long ksstatus; /* key server reply εtatus */ vme_t netname; /* netname */ long netnamelen; /* length of netname */ deε_block desblock; /* DES block in and out */ } KS DECRYPT T; typedef struct { K_MSGTYPE type; u_long rpcstatus; /* RPC status */ u_long ksstatuε; /* key server reply statuε */ vme_t netname; /* netname */ long netnamelen; /* length of netname */ unixcred cred; /* credentials returned */ } KS GETCRED T; c. Host Facility Communication Transactions The communication transactions that the host facility of the present invention recognizes and provides are summarized in Table 8 below. These transactionε are used to support the initialization and ongoing coordinated operation of the system 160. Table 8 Host Facility Message Types εc_regiεter_fifo SC_REGISTER_FIFO_T, *** ) ; εc_get_εyε_config SC_GET_SYS_CONFIG_T,***); sc_register_name SC_REGISTER_NAME_T, *** ) ; sc_init_complete SC_INIT_COMPLETE_T, *** ) ; sc__resolve_name SC_RESOLVE_NAME_T, *** ) ; εc_reεolve_fifo SC_RESOLVE_FIFO_T, *** ) ; εσ_time_register SC_TIME_REGISTER_T, *** ) ; sc__real_time SC_REAL_TIME_T, *** ) ; εc_err_log_msg SC_ERR_LOG_MSG_T,*** ) ; sc_err_log_msg2 SC ERR LOG MSG2,*** ); Name Service The name εerver daemon ("named") iε the Unix hoεt facility process that boots the system and understands all of the facility services that are present in the system. That is, each facility provides at least one service. In order for any facility to utilize a service of another, the name of that service must be published by way of registering the name with the name server daemon. A name is an ascii string that representε a service. When the name is registered, the relevant servicing process PID is also provided. Whenever the name server daemon iε thereafter queried to resolve a service name, the name server daemon will respond with the relevant procesε PID if the named service iε available. Thiε one level of indirection relieveε the need to otherwise establish fixed procesε IDs for all of the posεible services. Rather, the multi-tasking kernels of the messaging kernel layers are allowed to establiεh a PID of their own chooεing to each of the named services that they may register. The communication transaction: sc_regiεter_fifo ( SC_REGISTER_FIFO_T,*** ); iε directed to the named daemon of the host facility to provide notice that the issuing NC, FS, or S facility has been started. This transaction also identifies the name of the facility, as opposed to the name of a service, of the facility that is registering, its unique facility ID (VME εlot ID) and the shared memory addresε of itε meεεage deεcriptor FIFO. The communication transaction: εc_get_εys_config ( SC_GET_SYS_CONFIG_T,***); is used by a booting facility to obtain configuration information about the rest of the system 160 from the name server daemon. The reply mesεage identifies all -Ill- facilities that have been registered with the name server daemon. The communication transaction: εc_ini\ complete ( SC_INIT_COMPLETE_T, *** ); is sent to the name server daemon upon completion of its initialization inclusive of handling the reply message to its sc_get_sys_config transaction. When the name server daemon returns a reply message, the facility iε cleared to begin normal operation. The communication tranεaction: εc_register_name ( SC_REGISTER_NAME_T, *** ); is used to correlate a known name for a service with the particular PID of a facility that provides the service. The names of the typical services provided in the preferred embodiment of the present invention are listed in Table 9. Table 9 Named Facility Services Host Facility Resident SC_NAME_SERVER - the "Name server" daemon executes on the host peer-level processor, or primary host procesεor if there iε more than one host facility present in the system. Provides the syεtem wide name εervice. Operates also to collect and distribute information as to the configuration, both physical (the total number of NCs present in the system and the VME slot number of each) and logical (what system services are available) . SC_ERRD - the "ERRD" daemon - executes on the host peer-level processor, or primary host processor if there iε more than one hoεt facility preεent in the system. Injects an error message into the UNIX syslogd system. This results in the error mesεage being printed on the εyεtem conεole and, typically, logged it in an error file. SC_TIMED - the "TIMED" daemon - executes on the host peer-level processor, or primary host processor if there iε more than one hoεt facility present in the syεtem. Returnε the current εyεtem time. Can alεo be inεtructed to give notification of any εubsequent time changes. SC_KEYSERV - executes on the host peer-level processor, or primary host procesεor if there is more than one hoεt facility present in the system. When NFS runs in secure (DES encryption) mode, it provides accesε to the conventional Unix daemon that, in turn, provides acceεε to keyε which authenticate users. FS Facility Resident FC_VICE_PRES - executes on the FC peer-level processor, or primary FC processor if there is more than one such facility present in the system. Coordinates the operation of multiple FS facilities by εervicing all requeεts to identify the PID of the unnamed manager proceεs that controls access to a FSID. At least one unamed manager procesε runs in each FS facility. FC_STATMANS - executes in a respective FC facility (S) - Functions aε a "statistics manager" process on the FC facility to collect and allow other facilities to request a report of current statiεticε, εuch as the number of messages received. S Facility Resident S_MANAGERS - executes the ■ respective S facility (#). All low-level disk requeεts for the disk array coupled to the storage processor (S) are directed to this manager procesε. Unnamed worker processes are allocated, as necessary to actually carry out the request. S_STATMANS - executes in a respective S facility (S). Functions as a "statistics manager" process on the S facility to collect and allow other facilities to request a report of current statistics. NC Facility Resident NC_NFS_VPS - executes in a respective NC facility (S) • Controls the operation of NFS for itε reεpective NC facility. Acceptε meεsageε from the hoεt facility for starting and stoping NFS and for controlling the export and unexport of selected file systems. NC_DLCTRLS - executes in a respective NC facility (S). Functions as the Data Link controller for its NC facility (S). Accepts ioctl commands for a local message specified data link and allocates a worker process, aε necessary, to carry out the message request. NC_DLXMITS - executes in a respective NC facility (S)- Functions as the Data Link transmitter for its NC facility (S) . Acceptε transmit commands for a local message specified data link and allocates a worker process, as necessary, to carry out the message request. NC_STATMANS - executes in a respective NC facility (S). Functions as a "statistics manager" procesε on the NC facility to collect and allow other facilities to request a report of current statistics. The communication transaction: sc_reso1ve_name ( SC_RESOLVE_NAME_ , *** ) ; iε used by the mesεaging kernel layer of a facility to identify the relevant process PID of a service provided by another facility. The reply mesεage, when returned by the name server daemon, provides the "resolved" process ID or zero if the named service iε not supported. The communication transaction: sc_reεolve_fifo ( SC_RESOLVE_FIFO__T,*** ); is issued by a facility to the name server daemon the first time the facility needs to communicate with each of the other facilities. The reply message provided by the name server daemon identifies the shared memory address of the mesεage deεcriptor FIFO that correεponds to the named εervice. Time Service The time εerver daemon ("timed") provides syεtem wide timer εervices for all facilities. The communication transaction: sc_time_register ( SC_TIME_REGISTER_T,*** ) ; is issued by a facility to the timed daemon to determine the system time and to request periodic time synchronization messages. The reply message returns the current time. The communication tranεaction: sc_real_time ( SC_REAL_TIME_T, *** ); iε iεsued by the time server daemon to provide "periodic" time synchronization messages containing the current time. These transactions are directed to the requesting procesε, based the "client_pid" in the originally requesting message. The period of the transactions is a function of a default time period, typically on the order of several minutes, or whenever the syεtem time is manually changed. Error Logger Service The error server daemon ("errd") provides a convenient service to send error mesεages to the system console for all facilities. The communication tranεaction: sc_err__log_mεg ( SC_ERR_LOG_MSG_T, *** ); prints the string that is provided in the send message, while the transaction: εc_err_log_msg2 ( SC_ERR__LOG_MSG2, *** ) ; provides a message and an "error id" that specifieε a print format specification stored in an "errd message format" file. This format file may specify the error message format in multiple languages. /********************************************* * Structures and Constantε for the SC_NAMED proceεε ********************************************/ /* * Board typeε. */ Sdefine BT_NONE 0 Sdefine BT_UNIX 1 /* Host Processor */ Sdefine BT_PSA 2 /* Storage Processor */ Sdefine BT_FC 3 /* File Controller. */ Sdefine BT_NC 4 /* Network Controller. */ Sdefine BT_PLESSEY 5 /* Test Environment */ Sdefine BT_TRACE_ANAL 6 / * Mes sage Trace Analyzer. V Sdefine BT MEM 7 /* memory board. 7 * Slot deεcriptor. */ typedef εtruct { εhort board_type; εhort εlot_id; } SLOT DESC T; ************************************* * SC_NAMED: Typeε and εtructureε. ************************************ Sdefine SC_MSG_GROUP ( CC) ) << 16 ) Sdefine SC_REGISTER_FIFO Sdefine SC_RESOLVE_FIFO Sdefine SC_REGISTER_NAME Sdefine SC_RESOLVE_NAME Sdefine SC_DELAY Sdefine SC_GET_SYS_CONFIG Sdefine SC INIT COMPLETE Sdefine K MAX NAME LEN 32 /* Maximum proceεε name length. */ typedef struct { K_MSGTYPE type; short my_slot__id; short εender_slot_id; char name[K_MAX_NAME_LEN] ; M16_FIFO_DESC fifo_desc; short flags; /* flags defined below */ } SC_REGISTER_FIFO_T; /* * SC_REGISTER_FIFO_T flags: Sd Vefine NO_CM_ACCESS 1 /* can't access common memory */ typedef struct { K_MSGTYPE type; short my_slot_id; short dest_εlot_id; M16_FIFO_DESC fifo_deεc; /* 0 => not found */ } SC_RESOLVE_FIFO_T; typedef struct { K_MSGTYPE type; K_PID pid; char name[K_MAX_NAME_LE ] ; } SC_REGISTER_NAME_T; typedef struct { K_MSGTYPE type; K_PID pid; /* 0=) not found */ char name[K_MAX_NAME_LEN]; /* input */ } SC_RESOLVE_NAME_T; typedef struct { K_MSGTYPE type; SLOT_DESC_T config[M16_MAX_VSLOTS] ; } SC_GET_SYS_CONFIG_T; typedef struct { K_MSGTYPE type; short my_slot_id; } SC_INIT_COMPLETE_T; ********************************************* * SC_TIMED: Types and structures. ******************************************** / Sdefine SC_TIMED_REGISTER ( 101 | SC_MSG_GROUP ) Sdefine SC_REAL_TIME ( 102 j SC_MSG_GROUP ) typedef εtruct { K_MSGTYPE type; K_PID client__pid; long max_update__period; /* in εecondε. */ /* output */ long εecondε; /* seconds since Jan. 1, 1970 */ long micro_εeconds; /* and micro seconds. */ } SC_TIMED_REGISTER_T; typedef struct { K_MSGTYPE type; long seconds; /* seconds since Jan. 1, 1970 */ long micro_εeconds; /* and micro seconds. */ } SC_REAL_TIME_T; /************************************* * SC_ERRD: Types and Structures. ************************************ /* * SC_ERRD mesεage structures. * * Error log usage notes: * - Must include "syslog.h" * - Priority levels are: * LOG_EMERG system is unusable * LOG ALERT action must be taken immediately * LOG_CRIT critical conditions * LOG_ERR error conditions * LOG_WARNING warning conditions * LOG_NOTICE normal condition * LOG_INFO informational * LOG DEBUG debug-level messages * / Sdefine SC_ERR_LOG_MSG (301 j SC_MSG_GROUP ) Sdefine SC_ERR_LOG_MSG2 (302 J SC_MSG_GROUP ) Sdefine ERR_LOG_MSG_LEN (K_MSG_SIZE - sizeof(K_MSGTYPE) - sizeof(short) ) typedef struct { K_MSGTYPE type; /* SC_ERR_LOG_MSG */ short priority_level; char msg[ERR_LOG_MSG_LEN] ; /* meεsage } SC_ERR_LOG_MSG_T; typedef struct { K_MSGTYPE type; /* SC_ERR_LOG_MSG */ short id; /* Message id */ short filll; /* Unused. */ union { char c[80]; /* constants 7 short s[40]; long 1(20]; } data; } SC_ERR_LOG__MSG2_T; d. S Facility Communication Trans¬ actions The communication transactions that the S facilities of the present invention recognize, and that the other mesεaging kernel layers of the present invention recognize as appropriate to interact with the S facility, are summarized in Table 10 below. Table 10 Summary of S Communication Transactions sp_noop_mεg ( SP MSG,*** ); sp_send_config SEND_CONFIG_MSG, *** ) ; sp_receive_config RECEIVE_CONFIG_MSG, *** ); sp_r/w_εector SP_RDWR_MSG,*** ) ; εp_r/w_cache_pg SP_RDWR_MSG,*** ); εp_ioctl_req SP_IOCTL_MSG,*** ) ; sp_start_stop_msp SP_IOCTL_MSG,*** ) ; sp_inquiry_msg SP_MSG,*** ); sp_read_message_buffer_msg ( SP_MSG,*** ); εp_εet_εp_interrupt_msg (SP MSG,*** ); The S facility generally only reεponds to communication transactions initiated by other facil¬ ities. However, a few communication transactionε are initiated by the S facility at boot up aε part of the initial system configuration procesε. Each S facility meεsage utilizes the same block message structure of the FS and NC facility mesεageε. The firεt word provides a message type identifier. A second word is generally defined to return a completion status. Together, these words are defined by a SP HEADER structure: typedef { char reserved; char msg_code; char mεg_modifier; char memory_type; char complete_status; char bad_drive; char εense_key; char sense_code; } SP HEADER; The reserved byte will be used by the other facilities to identify a S facility message. Msg_code and mεg_modifier εpecify the S facility functionε to be performed. Memory_type εpecifieε the type of VME memory where data transfer takes place. The S facility uses this byte to determine the VMEbus protocolε to be uεed for data transfer. Memory_type iε defined as: 03 — Primary Memory, Enhanced Block Transfer 01 — Local Shared Memory, Block transfer 00 — Others, Non-block transfer The completion status word is used by the S facility to return mesεage completion εtatuε. The εtatuε word iε not written by the S facility if a message iε completed without error. One should zero out the completion status of a message before sending it to the S facility. When a reply is received, one examines the completion statuε word to differentiate a k_reply from a k__null_reply. The bad_drive value specifies any erroneous disk drive encountered. The higher order 4 bits specify the drive SCSI ID (hence, the drive set); the lower order 4 bits specify the S facility SCSI port number. The sense_key and senεe_code are conventional SCSI error identification data from the SCSI drive. The currently defined S facility functions, and identifying msg_code bytes are listed in Table 11. Table 11 Facility Message Types 01 — No Op 02 — Send Configuration Data 03 -- Receive Configuration Data 04 — S facility IFC Initialization 05 — Read and Write Sectors 06 — Read and Write Cache Pages 07 — IOCTL Operation 08 — Dump S facility Local RAM 09 — Start/Stop A SCSI Drive 0A — not used 0B — not used 0C — Inquiry 0D — not used 0E — Read Message Log Buffer OF — Set S facility Interrupt The message completion status word (byte 4-7 of a message) is defined as: Byte 00 — completion εtatuε 01 — SCSI device ID and S facility SCSI port number 02 — SCSI sense key 03 — SCSI sense code The completion status byte values are defined below: 00 -- Completed without error 01 — Reserved 02 — SCSI Status Error on IOCTL Mesεage 03 -- Reserved 04 — An inquired message is waiting to be executed 05 — An inquired mesεage iε not found 06 — VME data transfer error 07 — Reserved 08 — Invalid message parameter 09 -- Invalid data transfer count or VME data addreεε 0A — S facility configuration data not available 0B — Write protect or drive fault 0C — Drive off-line 0D -- Correctable data check 0E — Permanent drive error or SCSI interface error OF -- Unrecovered data check After receiving a meεεage, the S facility copies the contents into its memory. After a mesεage'ε function iε completed, a k_reply or k_null_reply iε uεed to inform the meεεage εender. K_null_reply iε uεed when the proceεsing is completed without error; k_reply is used when the processing is completed with error. When k_reply is used, a non-zero completion status word is written back to the original message. Therefore, when a reply is received, a message sender checks the status word to determine how a message is completed. When k_null_reply is used, the original mesεage is not updated. The S facility simply acknowledges the normal completion of a message. If a meεsage iε not directed to a diεk drive, it iε executed immediately. Diεk I/O meεsages are sorted and queued in disk arm elevator queues. Note, the INQUIRY mesεage returnε either 04 or 05 εtatus and uses k_reply only. No Qp The input parameters for this mesεage are defined aε: εp_noop_mεg ( SP_MSG,*** ); The only parameter needed for this mesεage is the message header. The purpose for this mesεage iε to teεt the communication path between the S facility and a message sender. A k_null_reply is always used. Send Configuration Data The input parameters for this operation are defined as: sp_send_config ( SEND_CONFIG_MSG,*** ) ; This message is used to inform the S facility about the operating parameters. It provides a pointer pointing to a configuration data structure. The S facility fetches the configuration data to initialize itε local RAM. The configuration data is also written to a reserved εector on each SCSI diεk εuch that they can be read back when the S facility is powered up. Hence, it -12.5- is not neceεεary to send this message each time the S facility is powered up. In the configuration data structure, vme_buε_re- quest_level specifies the S facility data transfer request level on the VME bus. The access_mode specifies if the S facility should run as independent SCSI drives or as a εingle logical drive. In the latter case, number_of_disks should be same as number_of_bankε because all nine drives in a bank are grouped into a εingle logical disk. Total_εector is the disk capacity of the attached SCSI diεks. Total capacity of a disk bank is this number multiplying the number_of_diskε. When addition¬ al disk banks are available, they could have sizes different from the first bank. Hence, total_sector is a three_entry array. Stripe_size is meaningful only when the S facility is running as a single logical disk storage subsystem. Different stripe sizes can be used for different drive banks. Finally, online_drive__bit_- map showε the drives that were online at the last reset. Bit 5 of online_drive_bit_map[ 1] being set indicates drive 5 of bank 1 is online. Total_sector and online_drive__bit_map could not and should not be specified by a user. The configuration data are written to the diεks in a S facility reserved sector, which is read at every S facuity reset and power up. When the configuration data are changed, one must reformat the S facility (erase the old file syεtemε). When this message is completed, a k_reply or k_null_reply is returned. Receive Configuration Data The input parameters for this operation are defined as: sp_receive_config ( RECEIVE_CONFIG_MSG, *** ); Thiε message requests the S facility to return configuration data to a mesεage εender. Vme_pointer εpecifies a VME memory location for εtoring the configuration data. The same configuration data structure specified n the last section will be returned. Read and Write Sectors The input parameters for thiε operation are defined as: sp_r/w_sector ( SP_RDWR_MSG,*** ); Unlike most S facility mesεageε, which are proceεsed immediately, this mesεage is first εorted and queued. Up to 200 messages can be sent to the S facility at one time. Up to thirty messages are executed on thirty SCSI drives simultaneouεly. The meεsages are sorted by their sector addresseε. Hence, they are not served by the order of their arrivals. There are two possible functions specified by thiε message: msg_mod = 00 — Sector Read = 01 — Sector Write ' Scsi_id εpecifies the drive set number. Disk_number specifies which SCSI port to be used. Sector_count specifies the number of disk sectorε to be transferred. For a εector_read mesεage, erase_sector_count specifieε the number of sectors in the VME memory to be padded with zeros (each sector is 512 bytes). For a sec- tor_write meεεage, eraεe_εector_count specifies the number of sectors on the diεk to be written with zeroε (hence, erased) . To prevent sectorε from being eraεed inadvertently, a εector_write meεsage can only specify one of the two counters to be non-zero, but not both. Sector_addresε εpecifies the diεk εector where read or write operation εtartε. Vme_addreεs specifies a starting VME memory location where data transfer takes place. There are three drive elevator queues maintained by the S facility for each SCSI port (or one for each disk drive) . The messages are inserted in the queue sorted by their sector addresses, and are executed by their orders in the queue. The S facility moves back and forth among queue entries like an elevator. This iε done to minimize the diεk arm movements . Separate queues for separate disk drives. These queues are processed currently because the SCSI drive disconnects from the bus whenever there is no data or command transfer activities on the buε. If no error conditions are detected from the SCSI drive(s), this mesεage iε completed normally. When data check iε found and the S facility is running as a εingle logical diεks, recovery actions using redundant data are started automatically. When a drive is down and the S facility is running as a single logical disk, recovery actions similar to data check recovery will take place. Other drive errors will be reported by a correεponding εtatuε code value. K_reply or K__null_reply is used to report the completion of this message. Read/Write Cache Pages The input parameters for this operation are defined as: εp_r/w_cache_pg ( SP_RDWR_MSG, *** ); This message is similar to Read and Write Sectorε, except multiple vme_addreεεes are provided for transferring disk data to and from disk sectors. Each vme_addresε points to a memory cache page, whose size is specified by cache_page_size. When reading, data are scattered to different cache pages; when writing, data are gathered from different cache pages (hence, it is referred to as scatter_gather function) . There are two poεsible functions specified by thiε mesεage; msg_mod = 00 -- Cache Page Read = 01 -- Cache Page Write Scsi_id, disk_number, sector_count, and sector_address are described in Read and Write Sector mesεage. Both sector_addresε and sector_count muεt be divisible by cache__page_size. Furthermore, sector_count must be less than 160 (or 10 cache pages) . Cache_page_εize specifies the number of sectorε for each cache page. Cache pageε are read or written sequentially on the drive(s) . Each page haε itε own VME memory addreεs. Up to 10 vme_addreεεes are specified. Note, the limit of 10 is set due to the size of a S facility meεsage. Like the sector read/write message, thiε message is also inserted in a drive elevator queue first. If no error conditions are detected from the SCSI drive(s), this message is completed normally. When an error is detected, a data recover action iε εtarted. When there iε a permanent drive error that prevents error recovery action from continuing, an error status code is reported as completion. K_reply or K_null_reply is used to report the completion of this message. IOCTL Request The input parameters for this operation are defined as: εp_ioctl_req ( SP_IOCTL_MSG,*** ); This message is used to addresε directly any SCSI disk or peripheral attached to a SCSI port. Multiple messages can be sent at the εame time. They are served in the order of first come first serve. No firmware error recovery action is attempted by the S facility. Scsi_id, scsi_port, and scsi_lun_address identify uniquely one attached SCSI peripheral device. Command_length and data_length εpecify the lengthε of command and data tranεfers reεpectively. Data_buffer- _addreεs pointε to a VME memory location for data transfer. The command_bytes are actual SCSI command data to be sent to the addressed SCSI peripheral device. Note, the data length must be multiples of 4 because the S facility always transfers 4 bytes at a time. Sense_length and εenεe_addr εpecify size and addresε of a piece of VME memory where device sense data can be stored in case of check statuε iε received. Theεe meεsages are served by the order of their arrivals. When this mesεage is terminated with drive error, a corresponding status code is returned. K_reply and k_null_reply are used to report the completion of thiε message. Start/Stop SCSI Drive 5 The input parameters for this operation are J defined as: εp_εtart_εtop_msp ( SP_IOCTL_MSG, *** ); This meεεage iε uεed to fence off any meεεage to a specified drive. It should be sent only when there is 10 no outstanding meεεage on the specified drive. Once a drive is fenced off, a message directed to the drive will receive a corresponding error statuε back. When the S facility iε running aε a single logical disk, this mesεage iε uεed to place a SCSI diεk drive 15 in or out of service. Once a drive is stopped, all operations to this drive will be fenced off. In such case, when the stopped drive is accessed, recovery actions are started automatically. When a drive is restarted, the data on the drive is automatically 20 reconfigured. The reconfiguration is performed whil.e the system is online by invoking recovery actions when the reconfigured drive is accessed. When a drive is reconfigured, the drive configura¬ tion sector is updated to indicate that the drive is 25 now a part of a drive set. * Messaoe Inquiry The input parameters for this message are defined as: εp__inquiry_msg ( SP_MSG,*** ); Thiε meεεage requests the S facility to return the statuε of a meεsage that was sent earlier. A k_reply is always used. The status of the meεsage, if available in the S facility buffers, is returned in the completion statuε word. Thiε meεsage is used to verify if a previous mesεage waε received by the S facility. If not, the message is lost. A lost mesεage εhould be resent. Message could be lost due to a local board reset. However, a mesεage εhould, in general, not be loεt. If meεεageε are loεt often, the S facility should be considered as broken and fenced off. Read Message Log The input parameters for this message are defined as: sp_read_message_buffer_msg ( SP_MSG,*** ); The S facility keeps a mesεage buffer which containε the laεt 200 messages. Data_buffer specifieε a piece of VME memory in which the messages are sent. Number_of__n.essage should not exceed 200. Each message is 128 bytes long as defined at the beginning of this Section. An application program must allocate a buffer big enough to accommodate all returned mesεageε. Normally this mesεage iε sent when there is no active messages. Otherwise, it iε very difficult to determine how many used meεsageε are in the S facility meεsage buffer. For example if there are 200 active messages, there will be no used ones in the message buffer. Where there are less than requested messages in the message buffer, 128 bytes of zeros are trans- mitted for each shortage. K_reply and k_null_reply are used for the completion of this message. SP__Interrupt The input parameters for thiε meεεage are defined as: εp_εet_εp_interrupt_mεg (SP_MSG,*** ); This mesεage tells the S facility to pass control to an on-board debug monitor, as present in the SP boot rom. After completing this message, the S facility no longer honors any messages until the monitor returns control. A k__null_reply is always returned for this mesεage. Th e S facility message structures are listed below: typedef struct pεa_mεg { /* A Mesεage Template */ } SEND CONFIG MSG; typedef εtruct { SP_HEADER header; /* byte 0-7 */ config_data *vme_pointer; long data__length; } RECEIVE CONFIG MSG; SP IOCTL MSG; IV. Start-up Operations A. IFC Initialization The chart below summarizeε the εyεtem operations that occur during syεtem boot. Table 12 Summary of System Initialization Phase 1: All peer-level processors { boot to "boot-level" ready state; } Phase 2: The host boot level facility { boot Unix image through boot-level S facility; execute Unix image; start SC_NAME_SERVER process; } Phase 3: The host facility { for each boot-level facility { probe for existence; initialize FIFO for receiving; } for each ( SP NC FC ) { read boot image and parameters from boot- level S facility; download boot image and boot parameters (including the PID of the SC_NAME_SERVER procesε) to the εhared memory program εtore of the peer-level processor; start controller; } } Phase 4: Each peer-level processor { begin executing facility image initialize controller { send SC_REG_FIFO to SC_NAME_SERVER; send SC_GET_SYS_CONF to SC_NAME_SERVER; send SC_INIT_CMPL to SC_NAME_SERVER; } start manager procesεeε { εend SC_REG_NAMEs to SC_NAME_SERVER; εend SC_RESOLVE_NAMEs to SC__NAME_SERVER; send SC_RESOLVE_FIFOs to SC_NAME_SERVER; } } The SP peer-level procesεors boot from onboard EPROMs. The SP boot program, in addition to providing for power-on diagnoεtics and initialization to a ready state, includes a complete S facility. Thus, the SP peer-level processor is able to perform SCSI disk and tape operations upon entering its ready state. In their ready states, the NC, FC, SP and H processors can be downloaded with a complete instantiation of their respective types of facilities. The downloaded program iε loaded into local shared memory; for the S facility, for example, the program is loaded into its local 256K static ram. The ram download, particularly to static ram, allowε both faεter facility execution and uεe of the latest release of the facility software. After powering up or resetting the SP processor, the host facility, executing itε boot program, waitε for the SP boot program to poεt ready by indicating a ready εtate value in an SP εtatuε regiεter. Once the S boot program has posted ready, a Sector Read message from the host boot program can be used to retrieve any disk block to any VME memory location. Generally, the read request is to load the host facility from disk block 0, the boot block. In preparing a read_sector meεsage for the S facility after power up, the local host boot program specifies the following (in addition to normal read_sector message contents): εender_pid=Oxffffffff dest_pid=0x00000001 By specifying the above, the local host boot program signals the S facility to bypass normal IFC reply protocols and to, in turn, εignal a reply complete by directly by changing the Oxffffffff message value in the original message image to any other value, such as the value of the meεsage deεcriptor. That iε, after building a read sector message, the host boot program writeε a meεsage deεcriptor to the S facility. The host boot program can then poll this sender_pid word to determine when the message is completed. Meεεageε to the S facility are εent in thiε manner until the full hoεt facility boot iε complete. Once the local hoεt boot program haε loaded the hoεt facility and begun executing itε initialization, the host facility generally εwitches over to normal IFC communication with the S facility. To do this, local host facility sends an IFC Initialization message to the S facility. After receiving this message, the S facility expectε a shared memory block, as specified by the message, to contain the following information: o Byte 00-03 - Bootlock, provides synchronization with the local host facility o Byte 04-05 — S facility board slot id, o Byte 06-07 — Reserved, o Byte 08-09 — Thiε board'ε IFC virtual εlot ID o Byte 10-11 -- System controller process number, o Byte 12-27 — System controller fifo descriptor Byte 00-01 — System controller fifo type, 5 Byte 02-03 -- System controller slot id Byte 04-07 — Fifo address Byte 08-09 — Soft fifo index, Byte 10-11 -- Soft fifo index mask, j Byte 12-13 — Interrupt request level, 10 Byte 14-15 — Interrupt vector addresε, o Byte 28-31 — Addresε of thiε common memory, and o Byte 32-35 — Size of this common memory. o Byte 36-39 — Hardware fifo addresε of the S facility 15 The firεt thing the S facility does is check the bootlock variable. When it is set to a "BOOTMASTER" value, it means the local host facility iε up and ready to receive meεεage from the S facility. Otherwiεe, the S facility waits for the local host facility to 20 complete its own initialization and set the bootlock word. As soon as the bootlock word iε changed, the S facility proceedε to perform IFC initialization. The following IFC messages are sent to the local host facility: 25 1. Register FIFO 2. Get System Configuration 3. Initialization Complete . Regiεter Name 5. Reεolve FIFO 30 The second mesεage allowε the S facility to know who is in what VME slots within the system. The S facility will only register one name, "SPn" (n is either 0 or 1), with a procesεor ID of 1. Hence all messages directed to the S facility specify PID SP__SLOT << 16 + 0x0001. Basically, a processor ID (PID) is a 4-byte word, in which the higher order two bytes contain the proceεεor'ε VME εlot ID. The lower order two byteε identify a process within a procesεor. The regiεter FIFO meεεage formally informε the local host facility about the S facility's fifo addreεε. The get εyεtem configuration meεεage retrieveε a table describing all available proσesεorε from the local host facility. After completing initialization, using the Initialization Complete message, the S facility advertiseε its serviceε by iεεuing the Register Name mesεage, which informs the hoεt facility that the S facility εervice procesε iε up and running. When another facility sends a message to the S facility for the first time, the S facility uses a Resolve FIFO message, directed to the host facility, to obtain the fifo address needed for a reply. * * * * * * * Thus, a multiple facility operating system architecture that provides for the control of an efficient, expandable multi-processor syεtem particularly suited to servicing large volumes of network file system requests has been described. Clearly, many modifications in variations of the preεent invention are possible in light of the above teachingε. Therefore, it is to be understood that within the scope of the appended claims, the principles of the present invention may be realized in embodiments other than aε εpecifically deεcribed herein.

Claims: Claims : 1. A computer syεtem employing a multiple facility operating εyεtem architecture, εaid computer system comprising: a) a plurality of processor units for implementing a predetermined set of peer-level facilities wherein each said peer-level facility includes a plurality of related functions, each said processor unit including: i) means for executing program instructions; and ii) means for storing program instrue- tions and data, εaid executing meanε being coupled to said storing means to permit the transfer of program instructionε and data, εaid εtoring meanε εtoring inεtructionε defining a predetermined peer-level facility of said predetermined set of peer-level facilities and instructionε for performing a multi- taεking interface function, said multi-tasking inter¬ face function being reεponsive to control mesεageε for selecting for execution functions of εaid predeter¬ mined peer-level facility and reεponsive to εaid predetermined peer-level facility for providing control meεsages to request or to respond to the performance of functions of another peer-level facility; and b) means for interconnecting εaid plurality of processor units, said interconnecting means providing for the transfer of control mesεageε between the multi-taεking interface funσtionε of said plurality of processor units.

Inventors: HARRIS GUY, HITZ DAVID, LAU JAMES, SCHWARTZ ALLAN, HARRIS, GUY, HITZ, DAVID, LAU, JAMES, SCHWARTZ, ALLAN
Applicants: AUSPEX SYSTEMS INC, AUSPEX SYSTEMS, INC.
Application year: 1990
Main classification: G06F13
IPC codes: G06F9, G06F13, G06F15