Abstract:
A software architecture for the hot add and swap of adapters. The software architecture allows users to replace failed components, upgrade outdated components, and add new functionality, such as new network interfaces, disk interface adapters and storage, without impacting existing users. The software architecture supports the hot add and swap of off-the-shelf adapters, including those adapters that are programmable.

Description:
COPYRIGHT RIGHTS  
         [0001]    A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The field of the invention relates to I/O adapters in computer systems. More particularly, the field of invention relates to the hot add and swap of adapters on a computer system.  
           [0004]    2. Description of the Related Technology  
           [0005]    As enterprise-class servers, which are central computers in a network that manage common data, become more powerful and more capable, they are also becoming ever more sophisticated and complex. For many companies, these changes lead to concerns over server reliability and manageability, particularly in light of the increasingly critical role of server-based applications. While in the past many systems administrators were comfortable with all of the various components that made up a standards-based network server, today&#39;s generation of servers can appear as an incomprehensible, unmanageable black box. Without visibility into the underlying behavior of the system, the administrator must “fly blind.” Too often, the only indicators the network manager has on the relative health of a particular server is whether or not it is running.  
           [0006]    It is well-acknowledged that there is a lack of reliability and availability of most standards-based servers. Server downtime, resulting either from hardware or software faults or from regular maintenance, continues to be a significant problem. By one estimate, the cost of downtime in mission critical environments has risen to an annual total of $4.0 billion for U.S. businesses, with the average downtime event resulting in a $140 thousand loss in the retail industry and a $450 thousand loss in the securities industry. It has been reported that companies lose as much as $250 thousand in employee productivity for every 1% of computer downtime. With emerging Internet, intranet and collaborative applications taking on more essential business roles every day, the cost of network server downtime will continue to spiral upward.  
           [0007]    A significant component of cost is hiring administration personnel. These costs decline dramatically when computer systems can be managed using a common set of tools, and where they don&#39;t require immediate attention when a failure occurs. Where a computer system can continue to operate even when components fail, and defer repair until a later time, administration costs become more manageable and predictable.  
           [0008]    While hardware fault tolerance is an important element of an overall high availability architecture, it is only one piece of the puzzle. Studies show that a significant percentage of network server downtime is caused by transient faults in the I/O subsystem. These faults may be due, for example, to the device driver, the device firmware, or hardware which does not properly handle concurrent errors, and often causes servers to crash or hang. The result is hours of downtime per failure, while a system administrator discovers the failure, takes some action, and manually reboots the server. In many cases, data volumes on hard disk drives become corrupt and must be repaired when the volume is mounted. A dismount-and-mount cycle may result from the lack of hot pluggability or hot plug in current standards-based servers. Hot plug refers to the addition and swapping of peripheral adapters to an operational computer system. Diagnosing intermittent errors can be a frustrating and time-consuming process. For a system to deliver consistently high availability, it must be resilient to these types of faults.  
           [0009]    Existing systems also do not have an interface to control the changing or addition of an adapter. Since any user on a network could be using a particular adapter on the server, system administrators need a software application that will control the flow of communications to an adapter before, during, and after a hot plug operation on an adapter.  
           [0010]    Current operating systems do not by themselves provide the support users need to hot add and swap an adapter. System users need software that will freeze and resume the communications of their adapters in a controlled fashion. The software needs to support the hot add of various peripheral adapters such as mass storage and network adapters. Additionally, the software should support adapters that are designed for various bus systems such as Peripheral Component Interconnect, CardBus, Microchannel, Industrial Standard Architecture (ISA), and Extended ISA (EISA). System users also need software to support the hot add and swap of canisters and multi-function adapter cards, which are plug-in cards having more than one adapter.  
           [0011]    In a typical PC-based server, upon the failure of an adapter, which is a printed circuit board containing microchips, the server must be powered down, the new adapter and adapter driver installed, the server powered back up and the operating system reconfigured.  
           [0012]    However, various entities have tried to implement the hot plug of these adapters to a fault tolerant computer system. One significant difficulty in designing a hot plug system is protecting the circuitry contained on the adapter from being short-circuited when an adapter is added to a powered system. Typically, an adapter contains edge connectors which are located on one side of the printed circuit board. These edge connectors allow power to transfer from the system bus to the adapter, as well as supplying data paths between the bus and the adapter. These edge connectors fit into a slot on the bus on the computer system. A traditional hardware solution for “hot plug” systems includes increasing the length of at least one ground contact of the adapter, so that the ground contact on the edge connector is the first connector to contact the bus on insertion of the I/O adapter and the last connector to contact the bus on removal of the adapter. An example of such a solution is described in U.S. Pat. No. 5,210,855 to Thomas M. Bartol.  
           [0013]    U.S. Pat. No. 5,579,491 to Jeffries discloses an alternative solution to the hot installation of I/O adapters. Here, each hotly installable adapter is configured with a user actuable initiator to request the hot removal of an adapter. The I/O adapter is first physically connected to a bus on the computer system. Subsequent to such connection a user toggles a switch on the I/O adapter which sends a signal to the bus controller. The signal indicates to the bus controller that the user has added an I/O adapter. The bus controller then alerts the user through a light emitting diode (LED) whether the adapter can be installed on the bus.  
           [0014]    However, the invention disclosed in the Jeffries patent also contains several limitations. It requires the physical modification of the adapter to be hotly installed. Another limitation is that the Jeffries patent does not teach the hot addition of new adapter controllers or bus systems. Moreover, the Jeffries patent requires that before an I/O adapter is removed, another I/O adapter must either be free and spare or free and redundant. Therefore, if there was no free adapter, hot removal of an adapter is impossible until the user added another adapter to the computer system.  
           [0015]    A related technology, not to be confused with hot plug systems, is Plug and Play defined by Microsoft and PC product vendors. Plug and Play is an architecture that facilitates the integration of PC hardware adapters to systems. Plug and Play adapters are able to identify themselves to the computer system after the user installs the adapter on the bus. Plug and Play adapters are also able to identify the hardware resources that they need for operation. Once this information is supplied to the operating system, the operating system can load the adapter drivers for the adapter that the user had added while the system was in a non-powered state. Plug and Play is used by both Windows 95 and Windows NT to configure adapter cards at boot-time. Plug and Play is also used by Windows 95 to configure devices in a docking station when a hot notebook computer is inserted into or removed from a docking station.  
           [0016]    Therefore, a need exists for improvements in server management which will result in continuous operation despite adapter failures. System users must be able to replace failed components, upgrade outdated components, and add new functionality, such as new network interfaces, disk interface adapters and storage, without impacting existing users. Additionally, system users need a process to hot add their legacy adapters, without purchasing new adapters that are specifically designed for hot plug. As system demands grow, organizations must frequently expand, or scale, their computing infrastructure, adding new processing power, memory, mass storage and network adapters. With demand for 24-hour access to critical, server-based information resources, planned system downtime for system service or expansion has become unacceptable.  
         SUMMARY OF THE INVENTION  
         [0017]    Embodiments of the inventive software architecture allows users to replace failed components, upgrade outdated components, and add new functionality, such as new network interfaces, disk interface adapters and storage, without impacting existing users. The software architecture supports the hot add and swap of off-the-shelf adapters, including those adapters that are programmable.  
           [0018]    One embodiment of the invention includes a method of hot swapping a programmable mass storage adapter connected to an operational computer, comprising: connecting the programmable mass storage adapter to a plurality of I/O devices, executing a statically loaded adapter driver which accepts a packet to suspend and restart communications to the mass storage adapter, suspending all communication to the programmable mass storage adapter, removing the programmable mass storage adapter, inserting a new programmable mass storage adapter into the computer and restarting communications between the computer and the new programmable mass storage adapter.  
           [0019]    Another embodiment of the invention includes a method of hot swapping a programmable mass storage adapter connected to an operational computer, comprising: connecting the programmable mass storage adapter to a plurality of I/O devices, executing a statically loaded adapter driver which accepts a packet to suspend and restart communications to the mass storage adapter, disabling power to the mass storage adapter, removing the mass storage adapter from the computer, inserting a new mass storage adapter into the computer at the same location as the mass storage adapter, enabling power to the new mass storage adapter and initiating communications between the computer and the new mass storage adapter.  
           [0020]    Yet another embodiment of the invention includes a method of hot swapping a mass storage adapter to an operational computer including at least one canister, wherein the canister connects to one or more existing programmable adapters, comprising: connecting the programmable adapters to a plurality of I/O devices, executing an adapter driver which accepts requests to suspend and restart communications to an adapter, suspending all communication to the existing adapters on a selected one of the canisters, disabling power to the selected canister with the existing adapters, while maintaining power to the computer and other adapters, removing a mass storage adapter in the canister, adding a new mass storage adapter in the canister, restarting power to the adapters in the canister, restarting communications to the existing adapters and initiating communications between the computer and the new mass storage adapter. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a top-level block diagram showing a fault tolerant computer system of one embodiment of the present invention, including a mass storage adapter and a network adapter.  
         [0022]    [0022]FIG. 2 is a block diagram showing a first embodiment of a multiple bus configuration connecting I/O adapters and a network of microcontrollers to the clustered CPUs of the fault tolerant computer system, shown in FIG. 1.  
         [0023]    [0023]FIG. 3 is a block diagram showing a second embodiment of a multiple bus configuration connecting canisters containing I/O adapters and a network of microcontrollers to the clustered CPUs of the fault tolerant computer system, shown in FIG. 1.  
         [0024]    [0024]FIG. 4 is a block diagram illustrating a portion of the fault tolerant computer system, shown in FIG. 1.  
         [0025]    [0025]FIG. 5 is a block diagram illustrating certain device driver components of the NetWare Operating System and one embodiment of a configuration manager which reside on the fault tolerant computer system, shown in FIG. 1.  
         [0026]    [0026]FIG. 6 is one embodiment of a flowchart illustrating the process by which a user performs a hot add of an adapter in the fault tolerant computer system, shown in FIG. 2.  
         [0027]    [0027]FIG. 7 is one embodiment of a flowchart showing the process by which a user performs a hot add of an adapter on a canister on a fault tolerant computer system, shown in FIG. 3.  
         [0028]    [0028]FIG. 8 is one embodiment of a flowchart showing the process by which a user performs a hot swap of an adapter on a fault tolerant computer system, shown in FIGS. 2 and 3.  
         [0029]    [0029]FIGS. 9A and 9B are flowcharts showing one process by which the configuration manager may suspend and restart I/O for hot swapping network adapters under the NetWare Operating System, shown in FIG. 8.  
         [0030]    [0030]FIGS. 10A, 10B and  10 C are flowcharts showing one process by which the configuration manager may suspend and restart I/O for mass hot swapping storage adapters under the NetWare Operating System, show in FIG. 8.  
         [0031]    [0031]FIG. 11 is a block diagram illustrating a portion of the Windows NT Operating System and a configuration manager which both reside on the fault tolerant computer system, shown in FIGS. 2 and 3.  
         [0032]    [0032]FIG. 12 is one embodiment of a flowchart showing the process by which the Windows NT Operating System initializes the adapter (miniport) drivers shown in FIG. 11 at boot time.  
         [0033]    [0033]FIG. 13 is a flowchart illustrating one embodiment of a process by which a loaded adapter driver of FIG. 12 initializes itself with the configuration manager under the Windows NT Operating System.  
         [0034]    [0034]FIG. 14 is one embodiment of a flowchart showing the process by which the configuration manager handles a request to perform the hot add of an adapter under the Windows NT Operating System, shown in FIG. 11.  
         [0035]    [0035]FIG. 15 is one embodiment of a flowchart showing the process by which an adapter driver locates and initializes a mass storage adapter under the Windows NT Operating System in the hot add process shown in FIG. 14.  
         [0036]    [0036]FIG. 16 is one embodiment of a flowchart showing the process by which the FindAdapter( ) routine initializes an adapter during the hot add locate and initialize process of FIG. 15.  
         [0037]    [0037]FIG. 17 is one embodiment of a flowchart showing the process by which the configuration manager suspends and resumes the state of an adapter under the Windows NT Operating System during the hot swap shown in FIG. 8. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    The following detailed description presents a description of certain specific embodiments of the present invention. However, the present invention can be embodied in a multitude of different ways as defined and covered by the claims. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout.  
         [0039]    [0039]FIG. 1 is a block diagram showing one embodiment of a fault tolerant computer system. Typically the computer system is one server in a network of servers and is communicating with client computers. Such a configuration of computers is often referred to as a client-server architecture. A fault tolerant server is useful for mission critical applications such as the securities business where any computer down time can result in catastrophic financial consequences. A fault tolerant computer will allow for a fault to be isolated and not propagate through the system thus providing complete or minimal disruption to continuing operation. Fault tolerant systems also provide redundant components, such as adapters, so service can continue even when one component fails.  
         [0040]    The system includes a fault tolerant computer system  100  connecting to a mass storage adapter  102  and a network adapter  104  such as for use in a Local Area Network (LAN). The mass storage adapter  102  may contain one or more of various types of device controllers: a magnetic disk controller  108  for magnetic disks  110 , an optical disk controller  112  for optical disks  114 , a magnetic tape controller  116  for magnetic tapes  118 , a printer controller  120  for various printers  122 , and any other type of controller  124  for other devices  126 . For such multi-function adapters, the controllers may be connected by a bus  106  such as a PCI bus. The peripheral devices communicate and are connected to each controller, by a mass storage bus. In one embodiment, the bus may be a Small Computer System Interface (SCSI) bus. In a typical server configuration there is more than one mass storage adapter connected to the computer  100 . Adapters and I/O devices are off-the-shelf products. For instance, sample vendors for a magnetic disk controller  108  and magnetic disks  110  include Qlogic, Intel, and Adaptec. Each magnetic hard disk may hold multiple Gigabytes of data.  
         [0041]    The network adapter  104  typically includes a network controller  128 . The network adapter  104 , which is sometimes referred to as a network interface card (NIC), allows digital communication between the fault tolerant computer system  100  and other computers (not shown) such as a network of servers via a connection  130 . In certain configurations there may be more than one network controller adapter connected to the computer  100 . For LAN embodiments of the network adapter, the protocol used may be, for example, Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), Fiber Distributed Datalink Interface (FDDI), Asynchronous Transfer Mode (ATM) or any other conventional protocol. Typically, the mass storage adapter  102  and the network adapter  104  are connected to the computer using a standards-based bus system. In different embodiments of the present invention, the standards based bus system could be Peripheral Component Interconnect (PCI), Microchannel, SCSI, Industrial Standard Architecture (ISA) and Extended ISA (EISA) architectures.  
         [0042]    [0042]FIG. 2 shows one embodiment of the bus structure of the fault tolerant computer system  100 . A number ‘n’ of central processing units (CPUs)  200  are connected through a host bus  202  to a memory controller  204 , which allows for access to memory by the other system components. In one embodiment, there are four CPUs  200 , each being an Intel Pentium Pro microprocessor. However, many other general purpose or special purpose parts and circuits could be used. A number of bridges  206 ,  208  and  209  connect the host bus to, respectively, three high speed I/O bus systems  212 ,  214 , and  216 . The bus systems  212 ,  214  and  216 , referred to as PC buses, may be any standards-based bus system such as PCI, ISA, EISA and Microchannel. In one embodiment of the invention, the bus system  212  is PCI. Alternative embodiments of the invention employ a proprietary bus. An ISA Bridge  218  is connected to the bus system  212  to support legacy devices such as a keyboard, one or more floppy disk drives and a mouse. A network of microcontrollers  225  is also interfaced to the ISA bus  226  to monitor and diagnose the environmental health of the fault tolerant system. A more detailed description of the microcontroller network  225  is contained in the U.S. patent application Ser. No. 08/942,402, “Diagnostic and Managing Distributed Processor System” to Johnson.  
         [0043]    A bridge  230  and a bridge  232  connects, respectively, the PC bus  214  with PC bus  234  and the PC bus  216  with the PC bus  236  to provide expansion slots for peripheral devices or adapters. Separating the devices  238  and  240 , respectively, on PC buses  234  and  236  reduces the potential that an adapter failure or other transient I/O error affect the entire bus and corrupt data, bring the entire system down or stop the system administrator from communicating with the system. The adapter devices  238  and  240  are electrically and mechanically connected to the PC buses  234  and  236  by PC slots such as slot  241 . Hence, an adapter is “plugged” into a slot. In one embodiment of the invention, each slot may be independently powered on and off.  
         [0044]    [0044]FIG. 3 shows an alternative bus structure embodiment of the fault tolerant computer system  100 . The two PC buses  214  and  216  contain a set of bridges  242 - 248  to a set of PC bus systems  250 - 256 . As with the PC buses  214  and  216 , the PC buses  250 - 256  can be designed according to any type of bus architecture including PCI, ISA, EISA, and Microchannel. The PC buses  250 - 256  are connected, respectively, to a canister  258 ,  260 ,  262  and  264 . The canisters  258 - 264  are casings for a detachable bus system and provide multiple PC slots  266  for adapters. In one embodiment, each canister may be independently powered on and off.  
         [0045]    [0045]FIG. 4 is a block diagram illustrating hardware and software components of the computer system  100  relating to hot plugging an adapter. A hot plug user interface  302  accepts requests by a user such as a system manager or administrator to perform the hot add or a hot swap of an adapter  310 . The user interface  302  preferably communicates through an industry standard operating system  304  such as Windows NT or NetWare, to the hot plug system driver  306  and an adapter driver  308 . In an alternative embodiment of the invention, a proprietary operating system may be utilized.  
         [0046]    The hot plug system driver  306  controls the adapter driver  308  for a hot plug operation. The hot plug system driver  306  stops and resumes the communications between the adapter  310  and the adapter driver  308 . During a hot add or swap of the adapter  310 , the hot plug hardware  312  deactivates the power to the PC slots  241  and  266  (FIGS. 2 and 3). One embodiment of the hot plug hardware  312  may include the network of microcontrollers  225  (FIGS. 2 and 3) to carry out this functionality.  
         [0047]    The adapter  310  could be any type of peripheral device such as a network adapter, a mass storage adapter, or a sound board. Typically, however, adapters involved in providing service to client computers over a network, such as mass storage, network and communications adapters, would be the primary candidates for hot swapping or adding in a fault tolerant computer system such as the computer system  100  (FIG. 1). The adapter  310  is physically connected to the hot plug hardware by PC slots such as slots  241  and  266  (FIGS. 2 and 3).  
         [0048]    [0048]FIGS. 6, 7, and  8  illustrate a generic process by which alternative embodiments of the present invention perform the hot add and swap of devices. Some embodiments of the invention use commercial operating systems, such as Macintosh O.S., OS/2, VMS, DOS, Windows 3.1/95/98 or UNIX to support hot add and swap.  
         [0049]    In alternative embodiments of the invention, the hot plug system executes on an I/O platform. In a first architectural embodiment of the invention, the I/O platform and its devices plug in as a single adapter card into a slot. In a second architectural embodiment of the invention, the bridge is integrated onto the motherboard, and hot plug adapters plug in behind the bridge. In a third architectural embodiment of the invention, the I/O platform is plugged in as an option to control non-intelligent devices as are recognized by skilled technologists.  
         [0050]    In the second architectural embodiment, the I/O platform can be any industry standard I/O board such as, for example, the 1Q80960RP Evaluation Board which is executing the Ix Works operating system by WindRiver Systems, Inc. In the second architectural embodiment, a hardware device module (HDM) or adapter driver executes on the motherboard. The HDM is designed to communicate via messages with any type of operating system executing on the computer. These messages correspond to primitives which allow hot add and hot swap of adapters plugged into the motherboard.  
         [0051]    The following sections describe embodiments of the invention operating on computers shown in FIGS. 2 and 3 under NetWare Operating System and Windows NT. As previously mentioned, FIGS. 6, 7, and  8  illustrate a generic process by which alternative embodiments of the present invention perform the hot add and swap of devices. First, a process for hot add and swap of an adapter under the NetWare Operating System will be described according to the processes shown in FIGS. 6, 7 and  8 . Second, a process for hot add and swap of an adapter  310  under the Windows NT Operating System environment will be described according to the processes shown in FIGS. 6, 7, and  8 .  
       Adapter Hot Plug with NetWare Operating System  
       [0052]    [0052]FIG. 5 is a block diagram illustrating the system components of the NetWare Operating System and an embodiment of the software components of the invention. A configuration manager  500  is responsible for managing all or some of the adapters on the PC buses  234  and  236  (FIG. 2), or  250 ,  252 ,  254  and  256  (FIG. 3). The configuration manager  500  keeps track of the configuration information for every managed adapter located on the fault tolerant computer system  100 . The configuration manager  500  also allocates resources for every managed adapter and initializes each managed adapter&#39;s registers during a hot swap operation. The registers of an adapter  310  are components or intermediate memories whose values issues a certain action in the adapter, or whose values indicate the status of the adapter.  
         [0053]    Novell has created two interfaces for adapter drivers to communicate with the NetWare Operating Systems (FIGS. 1 and 4). First, Novell has provided the Open Datalink Interface (ODI) for network drivers. Second, Novell has created the NetWare Peripheral Architecture (NWPA) for mass storage adapters. Each of these interfaces will be described below.  
         [0054]    With respect to network device drivers, such as a driver  524 , ODI was created to allow multiple LAN adapters, such as the adapter  104  to co-exist on network systems, and to facilitate the task of writing device driver software. The ODI specification describes the set of interface (FIG. 1) and software modules used by hardware vendors to interface with the NetWare operating system. At the core of the ODI is the link support layer (LSL)  502 . The LSL  502  is the interface between drivers and protocol stacks (not shown). Any LAN driver written to ODI specifications can communicate with any ODI protocol stack via the LSL  502 . A protocol stack is a layered communication architecture, whereby each layer has a well defined interface.  
         [0055]    Novell has provided a set of support modules that creates the interface to the LSL  502 . These modules are a collection of procedures, macros and structures. These modules are the media support module (MSM)  504  which contains general functions common to all drivers and the topology specific modules (TSM)  506 . The TSM  506  provides support for the standardized media types of token ring, Fiber Distributed Datalink Interface (FDDI) and Ethernet. The MSM  504  manages the details of interfacing ODI multi-link interface drivers (MLID) to the LSL  502  and the NetWare Operating System. The MSM  504  typically handles all of the generic initialization and run-time issues common to all drivers.  
         [0056]    The topology specific module or TSM  506  manages operations that are unique to a specific media type. The Hardware Specific Modules (HSM) are created by each adapter vendor for each type of adapter  308 . The HSM  508  contains the functionality to initialize, reset and shutdown the adapter  308 . The HSM  508  also handles packet transmission and reception to and from each adapter  308 .  
         [0057]    With respect to mass storage device drivers, such as a driver  526 , the NetWare Peripheral Architecture (NWPA)  510  is a software architecture developed by Novell which provides an interface for mass storage developers to interface with the NetWare operating system. The NWPA  510  is divided into two components: a host adapter module (HAM)  512  and a custom device module (CDM)  513 . The HAM  512  is a component that contains information on the host adapter hardware which is typically written by a mass storage adapter vendor. The CDM  513  is the component of the NWPA  510  that regulates the mass storage adapters  102 .  
         [0058]    The main purpose of the Filter CDM  516  is to locate each HAM  512 , register adapter events, and process the I/O suspend and I/O restart requests from the configuration manager  500 . These commands will be discussed in greater detail below with reference to FIG. 10.  
         [0059]    A NetWare user interface  518  initiates the requests to the configuration manager  500  to freeze and restart communications to a specified adapter  310 . A remote Simple Network Management Protocol (SNMP) agent  520  can also start the request to freeze and resume communications to the configuration manager  500  through a local SNMP agent  522 . SNMP is one of a set of protocols called TCP/IP, which is specifically designed for use in managing computer systems. In one embodiment of the invention, the computers would be similar to the fault tolerant computer system of FIG. 1 and connected in a server network via connection  130 .  
         [0060]    [0060]FIG. 6 is a flowchart illustrating one embodiment of the process to hot add an adapter  310 . For instance, the process shown in FIG. 6 may be utilized by a fault tolerant computer system  100  containing the bus structure shown in FIG. 2. The process described by FIG. 6 is generic to various implementations of the invention. The following description of FIG. 6 focuses on the hot add of an adapter  310  (FIG. 4) under the NetWare Operating System.  
         [0061]    Starting in state  600 , a user inserts an adapter  310  into one of the PC bus slots, such as the slot  241 . At this point, the hot plug hardware  312  has not turned on the power to the adapter&#39;s slot, although the fault tolerant computer system  100  is operational. Since the adapter&#39;s slot is not powered and is physically isolated from any other devices which are attached to the bus  234 , the adapter will not be damaged by a short circuit during the insertion process, and will not create problems for the normal operation of the fault tolerant computer system  100 . Moving to state  602 , the configuration manager  500  is notified that the adapter is now in the slot, and requests the hot plug hardware  312  to supply power to the adapter&#39;s slot. In one embodiment of the invention, the hot plug hardware automatically detects the presence of the newly added adapter  310  and informs the configuration manager  500 . In another embodiment of the invention, the user notifies the hot plug hardware  312  that the adapter  310  is connected to one of the PC slots  241 . The process by which a slot  241  and adapter  238  are powered on and attached to a shared bus  234  is described in the U.S. application Ser. No. 08/942,402, “Diagnostic and Managing Distributed Processor System” to Johnson.  
         [0062]    Once an adapter  310  is added to the computer system, system resources must be allocated for the adapter  310 . The configuration manager  500  then configures the newly added adapter  310  (state  604 ) by writing information to the adapters configuration space registers.  
         [0063]    Traditionally, an adapter,s resources are allocated by the Basic Input Output Services (BIOS). The BIOS are service routines which are invoked during the fault tolerant computers system=s 100 start up phase. The BIOS programs the I/O ports, or memory locations of each adapter on the fault tolerant computer system  100 . However, since any newly added adapter was not present during the execution of the BIOS initialization routines, the configuration manager  500  must configure the new adapter in the same manner that another like adapter is programmed by the BIOS. The process by which the configuration space of an a newly added adapter  310  is configured is described in the U.S. application Ser. No. 08/942,309, “Configuration Management Method for Hot Adding and Hot Replacing Devices” to Mahalingam.  
         [0064]    [0064]FIG. 7 is a flowchart illustrating the process hot add an adapter  310  on one of the canisters  258 - 264 . The process described by FIG. 7 is generic to multiple embodiments of the invention. For instance, the process shown in FIG. 7 is utilized by a fault tolerant computer system  100  containing the bus structure shown in FIG. 3. The following description of FIG. 7 focuses on the hot add of an adapter  310  on a canister under the NetWare Operating System.  
         [0065]    Starting in state  700 , all devices already operating in the selected canister are located, and activity involving those adapters is suspended. In one embodiment, the SNMP agent  520  or the NetWare User Interface  518  locates all devices, and initiates the request for the suspension for every adapter, such as the adapter  310 , on the canister. The configuration manager  500  suspends the I/O for every adapter that is located on the canister which was selected by the user to receive the new card. In another embodiment, the SNMP agent  520  or the NetWare User Interface  518  requests the configuration manager to suspend the canister. The configuration manager  500  then locates all devices and suspends the I/O for each adapter located on the selected canister.  
         [0066]    The configuration manager  500  initiates the suspension of I/O to either the NWPA  510  for the mass storage adapters  102  or the LSL  502  and MSM  504  for the network adapter  104 . FIGS. 9 and 10, described below, illustrate in detail the process by which the configuration manager  500  suspends and resumes the I/O to a mass storage adapter and to a network adapter.  
         [0067]    For the embodiments of the invention that use PCI, the bus must be quiesced, and power to the canister turned off. In one embodiment, the software must assert the bus reset bit as defined by the PCI specification (state  702 ). If the power to the canister is on, the hot plug hardware  312  is directed by the configuration manager  500  to disable the power to one of the specified canisters  258 - 264  (state  704 ). In another embodiment, the hot plug hardware  312  asserts bus reset, then powers the canister down.  
         [0068]    Proceeding to state  706 , the user removes the selected canister, e.g., canister  264 , and inserts an adapter into one of the PC slots  266 . If the card is on a new canister that was not present during boot initialization, the hot plug hardware  312  should support the sparse assignment of bus numbers for those systems that require such functionality. The user then returns the canister to the fault tolerant computer system  100 . The hot plug hardware  312  then restarts, at the request of the configuration manager  500 , the power to the selected canister (state  708 ). For PCI systems, the bus reset bit must be de-asserted (state  710 ). In one embodiment of the invention, this de-assertion is accomplished by the hot plug hardware. In another embodiment, the configuration manager  500  de-asserts the bus reset. The configuration manager  500  re-initializes the configuration space of each adapter that was previously in the system (state  712 ). Since an adapter has lost power during a hot add, the adapter is in an unknown state after reapplying power. Moving to state  714 , the configuration manager  500  programs the configuration space of the new adapter. Finally, the configuration manager  500  resumes operations to all of the adapters located on the canister (state  718 ). For mass storage adapters  102 , the configuration manager  500  notifies the NWPA  510  to resume communications. For network adapters  104 , the configuration manager  500  contacts the LSL  502  to resume communications. In some embodiments of the invention, the configuration manager  500  restarts I/O to all adapters in the canister, per such a request, while in other embodiments, the user interface  518  or SNMP agent  520  requests the configuration manger  500  to restart each adapter.  
         [0069]    [0069]FIG. 8 is a flowchart illustrating the process by which a user performs the hot swap of an adapter. The process described by FIG. 8 is generic to various implementations of the invention. For instance, the process shown in FIG. 8 may be utilized by a fault tolerant computer system  100  shown in FIGS. 2 and 3. The following description of FIG. 8 focuses on the hot swap of an adapter  310  under the NetWare Operating System.  
         [0070]    Before starting in state  800 , an event has occurred, such as a failure of an adapter, and the operator has been informed of the failure. The operator has procured a replacement part, and is determined to repair the computer system  100  at this time. The operator may have some other reason for deciding to remove and replace a card, such as upgrading to a new version of the card or its firmware. A user indicates his intention to swap an adapter through the NetWare user interface  518  or a remote SNMP agent  520  (FIG. 5).  
         [0071]    For the embodiment of the computer shown in FIG. 2, the configuration manager  500  suspends the communication between the adapter, which is to be swapped, and the adapter driver  308  (state  802 ). For the embodiment of the computer shown in FIG. 3, the configuration manager  500  freezes the communication to each adapter located on the same canister as the adapter to be swapped. FIGS. 9 and 10, described below, illustrate the process by which the communication is suspended and restarted for, respectively, a mass storage adapter and a network adapter.  
         [0072]    Next, in some embodiments, the hot plug hardware  318  asserts bus reset, if necessary, before removing power (state  804 ). In other embodiments, the configuration manager  500  specifically causes bus reset to be asserted before directing the hot plug hardware  318  to remove power. For embodiments of the computer shown in FIG. 2, the hot plug hardware  318  is then directed by the configuration manager  500  to suspend the power to the slot (state  806 ). For embodiments of the computer shown in FIG. 3, the hot plug hardware  318  is directed by the configuration manager  500  to suspend the power to adapter&#39;s canister (state  806 ).  
         [0073]    Proceeding to state  808 , for a canister system, the user removes the canister containing the failed card and exchanges an old adapter with a new adapter. The user then reinserts the canister. For a non-canister system, the user swaps the old adapter for the new adapter in the slot.  
         [0074]    For canister systems with a PCI bus, at state  810 , the hot plug hardware  318  reapplies power to the slot or the canister. For some embodiments, the hot plug hardware  312  also removes bus reset, if necessary, after applying power (state  812 ). In other embodiments, the configuration manager  500  must specifically de-assert the bus reset. For the embodiment of the computer shown by FIG. 2, the configuration manager  500  reprograms the configuration space of the replaced adapter to the same configuration as the old adapter (state  814 ). For the embodiment of the computer shown in FIG. 3, the configuration manager  500  reprograms the configuration space and resumes the communication of each adapter located on the canister on which the adapter was swapped (state  814 ). Finally in state  816  the configuration manager changes each adapter&#39;s state to active.  
         [0075]    [0075]FIGS. 9A and 9B illustrate the process by which the configuration manager  500  suspends and restarts the communication of a network adapter, such as the adapter  104 . The configuration manager  500  maintains information about the configuration space for each of the adapters maintained on the system. However, the configuration manager  500  does not know the logical number that the NetWare Operating System has assigned to each adapter. The configuration manager  500  needs the logical number of the adapter to direct the NetWare Operating System to shutdown a particular adapter. FIGS. 9A and 9B illustrate one embodiment of process of how the configuration manager  500  obtains the logical number of an adapter.  
         [0076]    Starting in a decision state  900  in FIG. 9A, the configuration manager  500  checks whether the adapter&#39;s class is of the type LAN (or network). For PCI systems, each adapter maintains information in its PCI configuration space indicating its class. If the configuration manager  500  identifies an adapter as being of the LAN class, the configuration manager  500  proceeds to state  902 . Otherwise, the configuration manager performs an alternative routine to handle the request to suspend or restart I/O communications (state  904 ). For example, if the class of the adapter  310  were of type “SCSI” (or mass storage), the configuration manager  500  would follow the process described in FIG. 10 for freezing the communication for a mass storage adapter  102 .  
         [0077]    As defined by the PCI specification, the base address registers (BARs) define the starting point of the I/O and memory addresses that each adapter has been allocated in system memory. Also, defined by the PCI specification, an adapter can have up to six BARs. It is up to the adapter vendor to implement one or more BARS in the adapter for I/O or memory addressing, as desired. According to the PCI specification, each of the six BAR entries in an adapter&#39;s configuration space is identified as to its resource type (bit zero indicates whether this BAR describes a memory space or I/O space).  
         [0078]    The configuration manager  500  reads all of the BARs in the configuration space for each adapter  310 , looking for a BAR which describes I/O resources. For each such BAR, the LSL  502  configuration spaces are searched for an I/O port address which matches this BAR. This process continues until a match is found, identifying the LSL  502  configuration space which describes this adapter. If no match is found, then LSL  502  has no logical board describing this adapter, and no driver exists to service this board.  
         [0079]    At state  902 , the variable “x” is initialized to zero. The xth BAR is examined to see if it is an I/O class address (states  906  and  908 ). If the BAR is not an I/O address, x is incremented (state  912 ), and a check is made whether all BARs have been examined (state  914 ). If all six BARs have now been examined (state  914 ), a status is returned by the configuration manager  500  indicating Adriver not loaded. Otherwise, the configuration manager  500  returns to state  908  to examine the next BAR.  
         [0080]    Referring to the state  910 , the configuration manager  500  assigns the variable “board_num” the value of zero. The configuration manager  500  uses the variable “board_num” when requesting information from the NetWare Operating System driver configuration tables. A driver configuration table describes what NetWare knows about a particular driver and the driver&#39;s adapter. At state  918 , the configuration manager  500  calls the NetWare Operating System to request the configuration table of the Aboard_num≅logical slot. The NetWare Operating Systems call to retrieve configuration table information is GetMLIDConfigurationTableEntry( ).  
         [0081]    If the configuration manager  500  call to GetMLIDConfigurationTableEntry( ) returns a configuration table, the configuration manager  500  compares the values of IOPort 0  and IOPort 1  fields of the configuration table, to the address located in the xth I/O BAR (state  908 ). If no match is found, the configuration manager  500  increments the board_num (state  924 ) and checks to see if any boards remain to be checked (state  926 ). If boards remain to be checked, the configuration manager proceeds back to state  918 . Otherwise, if all the boards have been checked, the configuration manager  500  proceeds to look for the next BAR (state  912 ). Maxlan-boards is a variable maintained by the NetWare Operating System indicating the maximum number of logical network adapters supported.  
         [0082]    If the BAR has a value equal to IOPort 0  or IOPort 1 , the current configuration table describes the requested adapter and the process proceeds to state  922 . The configuration manager  500  has at this point identified the logical board number of the adapter that the configuration manager  500  needs to shut down (state  922 ). The configuration manager  500  makes the NetWare Operating System call LSLGetMLIDControlEntry( ) to find an entry point into the adapter driver  308 . As part of the system call, the configuration manager  500  passes the logical board number as a parameter. The LSLGetMLIDControlEntry( ) system call returns a pointer to the DriverControl( ) entry point for the requested board. The DriverControl( ) entry to the HSM provides a means to quiesce or remove an instance of the driver. At a decision state  924 , the configuration manager  500  determines whether the user has requested a driver suspend or resume. If the user has requested driver suspend, the configuration manager  500  calls the DriverControl( ) entry point with the operation code ‘5’ (shutdown) requesting a temporary shutdown. The MSM  504  does not remove the adapter driver  308  from the memory, but leaves it in place and preserves its current state. The HSM  508  receives this call and shuts down all communication to the adapter. Otherwise, if the user has requested a driver resume, the configuration manager  500  calls DriverControl( ) entry point with the operation code ‘6’ (reset) state  928 . The HSM  508  receives this call and resets the adapter  310 . For both suspend and restart, the driver then proceeds to state  930  which returns a success message to the SNMP agent or NetWare user interface.  
         [0083]    [0083]FIGS. 10A, 10B and  10 C illustrate the process by which the filter CDM  513  (FIG. 5) and the configuration manager  500  freeze and resume the I/O to mass storage adapters such as the adapter  102 . FIG. 10A illustrates the initialization routine for the Filter CDM  513 .  
         [0084]    [0084]FIG. 10A describes the Filter CDM  513  initialization process. Starting in state  1000 , the NetWare Operating System starts the execution of Filter CDM  513 . The Filter CDM  513  obtains the physical PCI location of each adapter (state  1002 ). The Filter CDM obtains this information by making a Novell NetWare Operating System call named HAM_Return_Bus_Info( ). At state  1004 , the Filter CDM  513  registers the mass storage adapter  102  with the configuration manager  500 . The Filter CDM  513  also registers to receive AAdapter Attention events, to get notification from the NetWare Operating System when an adapter  310  fails. Finally, in state  1006 , the Filter CDM  513  waits for requests to suspend and restart the I/O from the configuration manager  500 .  
         [0085]    [0085]FIG. 10B illustrates the process by which the configuration manager  500  and the Filter CDM  513 , shown in FIG. 5, suspend the I/O to a mass storage adapter. At state  900  (FIG. 9A), the configuration manager  500  has determined that the current suspend or restart request applies to a mass storage adapter, and proceeds to state  904 . If the request is a suspend request, the configuration manager  500  proceeds to state  1008  (FIG. 10B). If the request is a restart, the configuration manager  500  proceeds to state  1030  (FIG. 10C).  
         [0086]    The configuration manager  500  receives the request and generates a packet to suspend I/O (state  1010 ). The suspended I/O packet contains instructions to the Filter CDM  513  to freeze a particular mass storage adapter. The Filter CDM  513  receives the packet from the configuration manager  500  (state  1012 ). The Filter CDM  513  then makes a NetWare Operating System call to the NPA_Config( ) routine. The NPA_Config( ) routine halts all communication to a specified mass storage adapter  108  at the NWPA  510 .  
         [0087]    The NPA_Config( ) routine also determines if all pending requests have been processed or not. At state  1014 , the Filter CDM  513  starts a counter. The Filter CDM  513  uses this counter to ascertain whether the mass storage adapter  102  is malfunctioning as will be explained below. The Filter CDM  513  queries the NPA_Config( ) routine to find the number of outstanding I/O requests to a specified mass storage adapter (decision state  1018 ). If the Filter CDM  513  finds that the number of pending I/O requests to a particular mass storage adapter is zero, the Filter CDM  513  proceeds to notify the HAM  512  that the adapter is about to be powered down by the call HAM Suspension_Notification( ) (state  1020 ). If the number of requests pending on an adapter is not zero, the Filter CDM  513  checks to see if the counter is down to zero (decision state  1022 ). If the counter is not zero, the Filter CDM  513  decrements the counter (state  1024 ). The Filter CDM  513  repeats the process of reading the outstanding I/O (state  1016 ) until there are zero I/Os pending on the mass storage adapter or the counter reaches zero (state  1026 ). If the counter reaches zero, the Filter CDM  513  assumes that the mass storage adapter is malfunctioning (state  1026 ). The Filter CDM  513  proceeds to shut down the mass storage adapter, losing the pending I/Os (state  1020 ). After the Filter CDM  513  shuts down the adapter, the Filter CDM  513  relays the status of the I/O suspension to the configuration manager  500  (state  1028 ).  
         [0088]    Referring to FIG. 10C, states  1030  to  1036  describe the process by which the communication between the mass storage adapter and an adapter driver is restarted. At state  1030 , a request is made to restart the I/O. Next, the configuration manager  500  generates a restart I/O packet (state  1032 ). The configuration manager  500  sends this packet to the Filter CDM  513 . The Filter CDM  513  receives this I/O packet to restart the communication between the mass storage adapter and the adapter driver (state  1034 ). The Filter CDM  513  makes a call to NPA_Config( ) to restart the communication between the mass storage adapter and the adapter driver. After the resumption of communication to the mass storage adapter  102 , the Filter CDM  513  returns completion status to the configuration manager  500  (state  1036 ).  
       Adapter Hot Plug Under the Windows NT Operating System  
       [0089]    [0089]FIG. 11 is a block diagram illustrating various components of one embodiment of the hot plug adapter invention as implemented under the Windows NT Operating System (WinNT). A configuration manager  1100  controls the process of hot adding and swapping an adapter. An administrative agent  1103  initiates requests to the configuration manager  1100  and the network of microcontrollers  225  to oversee the process of hot add and swap of an adapter. The administrative agent  1103  initiates requests to the configuration manager  1100  to suspend and restart the communications of an adapter  310 . The administrative agent  1103  initiates requests to the microcontroller network device driver  1102  to turn on and off the power to the slots  241  and  266  (FIGS. 2 and 3). The network of microcontrollers  225  is one way of implementing the hot plug hardware  312  (FIG. 4).  
         [0090]    The configuration manager  1100  controls the communication between each adapter and adapter driver by calling the SCSI port  1104  and NDIS  1105 . SCSI port and NDIS are interfaces which are exported by the Windows NT Operating system. These interfaces are designed to interact with a miniport  1106  which is an instance of an adapter driver  308 . In Windows NT, each adapter will have its own miniport.  
         [0091]    As previously mentioned, FIGS. 6, 7 and  8  illustrate a generic process by which alternative embodiments of the present invention may perform the hot add and swap of adapters. FIGS. 6, 7 and  8  describe not only the hot add and swap process under the NetWare Operating System, but they also describe the hot add and swap process under Windows NT Operating System (WinNT). FIGS. 12 through 17 focus on the process by which the hot add and swap process shown in FIGS. 6, 7, and  8  may be implemented using the WinNT.  
         [0092]    [0092]FIG. 12 is a flowchart showing one embodiment of the process by which WinNT loads each adapter driver at system boot time. WinNT maintains an ordered list of adapter drivers that are registered with the operating system. This list determines the order in which each adapter gets initialized by WinNT. In one embodiment of the invention the configuration manager  1100  is registered to load first at state  1200 . Installation software has modified the list of adapter drivers to load the configuration manager  1100  first, so that the other adapter drivers can register with the configuration manager  1100  during their initialization. Moving to state  1202 , WinNT proceeds to load the mass storage driver. Traditionally, the adapter driver for one or more the mass storage adapters is the first adapter driver loaded by WinNT, so that other drivers have access to a mass storage medium. WinNT then loads the remainder of the drivers (state  1204 ).  
         [0093]    [0093]FIG. 13 is a block diagram illustrating one embodiment of the method by which an adapter driver registers with the configuration manager  1100  during its initialization. Starting at state  1300 , WinNT performs the standard adapter driver initialization by calling the DeviceEntry( ) function for each adapter driver. At state  1302 , the adapter driver&#39;s DeviceEntry( ) opens a configuration manager device object. The configuration manager  1100  device object is a “handle” by which software, such as the adapter driver  1106 , can communicate with the configuration manager  1100 . The adapter driver  1106  sends a request to the configuration manager  1100  to register the adapter driver  1106  with the configuration manager  1100  (state  1304 ). The adapter driver  1106  communicates with the configuration manager  1100  by a predefined dispatch routine. The method of creating a Windows NT dispatch routine is described in the AWindows NT Device Driver Book, by Art Baker, at pages 163 to 179 which are hereby incorporated by reference.  
         [0094]    At state  1306 , the adapter driver such as driver  308  sets an asynchronous I/O Request Packet (IRP) for rescanning. The I/O Request Packet is a data structure defined by the Windows NT Operating System. The adapter driver  308  allocates and registers an IRP with the Windows NT operating system. The rescan IRP contains a pointer to completion routine within the adapter driver  308 . The adapter driver  308  sets the completion routine to a procedure which scans for and initializes an adapter  310 . During a hot add of an adapter, the initialization routine is called by the configuration manager  1100  to configure the adapter state. Still at state  1306 , the adapter driver  308  calls to the SCSI port  1104  to finish the adapter&#39;s initialization  
         [0095]    Next, the SCSI port  1104  searches the bus for an adapter  310  (decision state  1308 ). If the SCSI port  1104  finds an adapter  310 , the SCSI port  1104  calls each driver=s FindAdapter( ) routine (state  1312 ). In addition to performing the traditional functions of the FindAdapter( ) routine, FindAdapter( ) registers each found adapter  310  with the configuration manager  1100 . The configuration manager  1100  then retrieves the configuration information of the adapter  310 . The configuration manager  1100  saves the configuration information for each adapter  310  in a linked list of data. The configuration manager  1100  maintains this linked list of data in case an adapter  310  fails. Upon the failure of an adapter  310 , the configuration manager  1100  reprograms a replacement adapter&#39;s configuration space.  
         [0096]    After finding an adapter  310  on the bus, the SCSI port  1104  returns to search for additional adapters  310  (decision state  1308 ). Once the SCSI port  1104  configures all of the adapters  310 , the SCSI port  1104  ends (state  1310 ).  
         [0097]    [0097]FIG. 14 is a flowchart illustrating the process by which one embodiment of the configuration manager  1100  handles a request to configure a hotly added adapter  310 . FIG. 14 is a more detailed description of state  604  shown in FIG. 6 and the state  714  shown in FIG. 7.  
         [0098]    Starting at state  1400 , the configuration manager  1100  reads the vendor and adapter ID of the adapter  310  that has been hotly added. The vendor and adapter ID are typically maintained in Read Only Memory (ROM) on an adapter  310 .  
         [0099]    Moving to state  1402 , the configuration manager  1100  makes an internal check to see if an adapter driver  308  had previously registered with the configuration manager  1100 . If no adapter driver  308  registered for this adapter  310 , the configuration manager  1100  returns an error (state  1404 ). Otherwise, if there is a driver registered for the adapter  310 , the configuration manager, programs the bus, system and operating system adapter information (state  1406 ).  
         [0100]    In one embodiment of the invention, the configuration information is calculated on an ad-hoc basis. In another implementation of the invention, the configuration information is maintained in a template. The template is based upon the configuration information of an adapter of the same type located on a reference system. The reference system is another fault tolerant computer system. After following the traditional initialization process of an adapter, a snapshot is taken of the configuration space for each adapter of the PC buses  241  and  256  (FIGS. 2 and 3). The snapshot of the configuration space for each adapter is used to build a template which is incorporated into the configuration manager  1100 .  
         [0101]    Once the configuration space of the adapter  310  is initialized, the configuration manager  1100  completes the adapter initialization (state  1408 ). Although the configuration space of the adapter  310  is finished, the adapter driver  308  completes the initialization process by configuring any adapter specific requirements. For example, SCSI adapters often contain a microcontroller for controlling an SCSI bus. The adapter driver  308  initializes this microcontroller (state  1408 ). The process by which the configuration manager  1100  returns control to the adapter driver  308  is by calling the completion routine of the rescan IRP that the adapter driver  308  created during the adapter driver&#39;s initialization.  
         [0102]    [0102]FIG. 15 is a flowchart illustrating one embodiment of the process by which the adapter driver such as the driver  308  finishes initializing a hotly added adapter such as the adapter  310 . The configuration manager  1100  calls the adapter driver through the rescan completion routine that the adapter driver  308  created during its initialization (state  1508 ). The adapter driver  308  then calls the SCSI port&#39;s initialize routine, SCSIportInitalize( ). The SCSI port locates the new adapter  310  (state  1502 ). The SCSI port  1104  calls the FindAdapter( ) routine for each adapter driver  308  in the  1106  (state  1504 ). The adapter driver  308  then creates a new asynchronous rescan IRP for the next occurrence of a hot add of an adapter (state  1506 ).  
         [0103]    [0103]FIG. 16 is a flowchart showing one embodiment of the process by which the FindAdapter( ) routine for an adapter handles a hot add request. FIG. 16 provides a more detailed explanation of the state  1504  shown in FIG. 15. Starting in state  1600 , the FindAdapter( ) routine performs the traditional initialization functions that are associated with the routine. For example, in a Qlogic PCI SCSI adapter the FindAdapter( ) routine reads the configuration information, maps the I/O registers for the adapter, resets the microcontroller on the adapter, checks the SCSI ID, and initializes the virtual and physical queue addresses.  
         [0104]    Moving to state  1602 , the FindAdapter( ) routine performs some optional adapter diagnostics. If the adapter  310  performs the diagnostics and the adapter  310  finds an error, the FindAdapter( ) routine proceeds to state  1604 . Otherwise, if no error was found, the FindAdapter( ) routine sends an IRP to the configuration manager  1100  creating a Device Instance for the newly hot added card ( 1606 ). The configuration manager  1100  sends an asynchronous device state IRP (state  1608 ). The configuration manager  1100  calls the completion routine of the device state IRP when the user has requested a hot swap.  
         [0105]    [0105]FIG. 17 is a flowchart illustrating one embodiment of the process by which the configuration manager  1100  suspends and restarts the state of an adapter  310  under WinNT. Starting at state  1700 , a user, through an administrative agent  1103 , requests to suspend or restart communications to a specified adapter  310 . Moving to state  1702 , the configuration manager  1100  records the new state of the adapter  310 . The configuration manager  1100  then finds and calls the device state IRP&#39;s completion routine of the adapter  310 . The configuration manager  1100  finds the correct completion routine by examining each of the device state IRPs posted by the adapter drivers  308 .  
         [0106]    The completion routine then determines whether the user has requested to suspend or resume an adapter  310  state (decision state  1704 ). If a user requests to restart an adapter  310 , the completion routine calls the adapter driver&#39;s reinitialize routine (state  1706 ). Otherwise, if the user requests to suspend an adapter  310 , the completion routine calls the driver&#39;s suspend routine (state  1708 ). After an adapter&#39;s re-initialization (state  1706 ) or suspension (state  1708 ), the adapter driver  308  creates another device state IRP ( 1710 ). The configuration manager  1100  uses the completion routine of this IRP to call the adapter driver  308  to change the state of the adapter  310  at a later point in time for future hot swaps. The configuration manager  1100  then notifies the user of the result of the user&#39;s request to suspend or resume an adapter  310  (state  1712 ).  
         [0107]    While the above detailed description has shown, described, and pointed out the fundamental novel features of the invention as applied to various embodiments, it will be understood that various omissions and substitutions and changes in the form and details of the system illustrated can be made by those skilled in the art, without departing from the intent of the invention.  
       Appendix A  
     Incorporation by Reference of Commonly Owned Applications  
       [0108]    The following patent applications, commonly owned and filed Oct. 1, 1997, are hereby incorporated herein in their entirety by reference thereto:  
                                                       Attorney Docket       Title   Application No.   U.S. Pat. No.   No.                   “System Architecture for Remote   08/942,160       MNFRAME.002A1       Access and Control of       Environmental Management”       “Method of Remote Access and   08/942,215   6,189,109   MNFRAME.002A2       Control of Environmental       Management”       “System for Independent Powering   08/942,410   6,202,160   MNFRAME.002A3       of Diagnostic Processes on a       Computer System”       “Method of Independent Powering   08/942,320   6,134,668   MNFRAME.002A4       of Diagnostic Processes on a       Computer System”       “Diagnostic and Managing   08/942,402       MNFRAME.005A1       Distributed Processor System”       “Method for Managing a   08/942,448       MNFRAME.005A2       Distributed Processor System”       “System for Mapping   08/942,222   6,122,758   MNFRAME.005A3       Environmental Resources to       Memory for Program Access”       “Method for Mapping   08/942,214   6,199,173   MNFRAME.005A4       Environmental Resources to       Memory for Program Access”   08/942,309       MNFRAME.006A1       “Hot Add of Devices Software       Architecture”       “Method for The Hot Add of   08/942,306       MNFRAME.006A2       Devices”       “Hot Swap of Devices Software   08/942,311   6,192,434   MNFRAME.006A3       Architecture”       “Method for The Hot Swap of   08/942,457       MNFRAME.006A4       Devices”       “Method for the Hot Add of a   08/943,072   5,892,928   MNFRAME.006A5       Network Adapter on a System       Including a Dynamically Loaded       Adapter Driver”       “Method for the Hot Add of a   08/942,069   6,219,734   MNFRAME.006A6       Mass Storage Adapter on a System       Including a Statically Loaded       Adapter Driver”       “Method for the Hot Add of a   08/942,465   6,202,111   MNFRAME.006A7       Network Adapter on a System       Including a Statically Loaded       Adapter Driver”       “Method for the Hot Add of a   08/962,963   6,179,486   MNFRAME.006A8       Mass Storage Adapter on a System       Including a Dynamically Loaded       Adapter Driver”       “Method for the Hot Swap of a   08/943,078   5,889,965   MNFRAME.006A9       Network Adapter on a System       Including a Dynamically Loaded       Adapter Driver”       “Method for the Hot Swap of a   08/942,336       MNFRAME.006A10       Mass Storage Adapter on a System       Including a Statically Loaded       Adapter Driver”       “Method for the Hot Swap of a   08/942,459   6,170,028   MNFRAME.006A11       Network Adapter on a System       Including a Statically Loaded       Adapter Driver”       “Method for the Hot Swap of a   08/942,458   6,173,346   MNFRAME.006A12       Mass Storage Adapter on a System       Including a Dynamically Loaded       Adapter Driver”       “Method of Performing an   08/942,463   6,035,420   MNFRAME.008A       Extensive Diagnostic Test in       Conjunction with a BIOS Test       Routine”       “Apparatus for Performing an   08/942,163   6,009,541   MNFRAME.009A       Extensive Diagnostic Test in       Conjunction with a BIOS Test       Routine”       “Configuration Management       Method for Hot Adding and Hot       Replacing Devices”   08/941,268   6,148,355   MNFRAME.010A       “Configuration Management   08/942,408   6,243,773   MNFRAME.011A       System for Hot Adding and Hot       Replacing Devices”       “Apparatus for Interfacing Buses”   08/942,382   6,182,180   MNFRAME.012A       “Method for Interfacing Buses”   08/942,413   5,987,554   MNFRAME.013A       “Computer Fan Speed Control   08/942,447   5,990,582   MNFRAME.016A       Device”       ”Computer Fan Speed Control   08/942,216   5,962,933   MNFRAME.017A       Method”       “System for Powering Up and   08/943,076   6,122,746   MNFRAME.018A       Powering Down a Server”       “Method of Powering Up and   08/943,077   6,163,849   MNFRAME.019A       Powering Down a Server”       “System for Resetting a Server”   08/942,333   6,065,053   MNFRAME.020A       “Method of Resetting a Server”   08/942,405       MNFRAME.021A       “System for Displaying Flight   08/942,070   6,138,250   MNFRAME.022A       Recorder”       “Method of Displaying Flight   08/942,068   6,073,255   MNFRAME.023A       Recorder”       “Synchronous Communication   08/943,355   6,219,711   MNFRAME.024A       Interface”       “Synchronous Communication   08/942,004   6,068,661   MNFRAME.025A       Emulation”       “Software System Facilitating the   08/942,317   6,134,615   MNFRAME.026A       Replacement or Insertion of       Devices in a Computer System”       “Method for Facilitating the   08/942,316   6,134,614   MNFRAME.027A       Replacement or Insertion of       Devices in a Computer System”       “System Management Graphical   08/943,357       MNFRAME.028A       User Interface”       “Display of System Information”   08/942,195   6,046,742   MNFRAME.029A       “Data Management System   08/942,129   6,105,089   MNFRAME.030A       Supporting Hot Plug Operations on       a Computer”       “Data Management Method   08/942,124   6,058,445   MNFRAME.031A       Supporting Hot Plug Operations on       a Computer”       “Alert Configurator and Manager”   08/942,005       MNFRAME.032A       “Managing Computer System   08/943,356       MNFRAME.033A       Alerts”       “Computer Fan Speed Control   08/940,301       MNFRAME.034A       System”       “Computer Fan Speed Control   08/941,267       MNFRAME.035A       System Method”       “Black Box Recorder for   08/942,381       MNFRAME.036A       Information System Events”       “Method of Recording Information   08/942,164       MNFRAME.037A       System Events”       “Method for Automatically   08/942,168   6,243,838   MNFRAME.040A       Reporting a System Failure in a       Server”       “System for Automatically   08/942,384   6,170,067   MNFRAME.041A       Reporting a System Failure in a       Server”       “Expansion of PCI Bus Loading   08/942,404       MNFRAME.042A       Capacity”       “Method for Expanding PCI Bus   08/942,223   6,195,717   MNFRAME.043A       Loading Capacity”       “System for Displaying System   08/942,347   6,145,098   MNFRAME.044A       Status”       “Method of Displaying System   08/942,071   6,088,816   MNFRAME.045A       Status”       “Fault Tolerant Computer System”   08/942,194   6,175,490   MNFRAME.046A       “Method for Hot Swapping of   08/943,044       MNFRAME.047A       Network Components”       “A Method for Communicating a   08/942,221   6,163,853   MNFRAME.048A       Software Generated Pulse       Waveform Between Two Servers       in a Network”       “A System for Communicating a   08/942,409       MNFRAME.049A       Software Generated Pulse       Waveform Between Two Servers       in a Network”       “Method for Clustering Software   08/942,318   6,134,673   MNFRAME.050A       Applications”       “System for Clustering Software   08/942,411       MNFRAME.051A       Applications”       “Method for Automatically   08/942,319   6,212,585   MNFRAME.052A       Configuring a Server after Hot       Add of a Device”       “System for Automatically   08/942,331       MNFRAME.053A       Configuring a Server after Hot       Add of a Device”       “Method of Automatically   08/942,412   6,154,835   MNFRAME.054A       Configuring and Formatting a       Computer System and Installing       Software”       “System for Automatically   08/941,955   6,138,179   MNFRAME.055A       Configuring and Formatting a       Computer System and Installing       Software”       “Determining Slot Numbers in a   08/942,462       MNFRAME.056A       Computer”       “System for Detecting Errors in a   08/942,169       MNFRAME.058A       Network”       “Method of Detecting Errors in a   08/940,302       MNFRAME.059A       Network”       “System for Detecting Network   08/942,407       MNFRAME.060A       Errors”       “Method of Detecting Network   08/942,573       MNFRAME.061A       Errors”