Abstract:
A method for writing file data from client to server which comprises writing file data from a client to a server, wherein the client issues to the server a file transfer proposal that includes the names of a plurality of files to be transferred and attributes of each of the plurality of files. The server determines optimum memory locations for the plurality of files and optimum sequence and size of data transfer and issues to the client a request to transfer the plurality of files in a sequence that is optimized for memory location and minimal number of data transfers, thereby maximizing data transfer rate from the client to the server. Client computer, server computer, and network apparatus that are configured to implement the method are also disclosed.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/276,829, filed Mar. 16, 2001, which is herein incorporated by reference in its entirety. 

   BACKGROUND 
   1. Field of the Invention 
   The present invention relates to the field of storage area networks serving computer file server systems and client computers, and more particularly, to methods of transferring data between the client and server. 
   2. Background of the Invention 
     FIG. 1  shows a typical storage area network  100  serving client computer  102  and computer file server system  104 . Client  102  and server  104  are in communication via network  106 . 
   Client computer  102  can include a processor  108  coupled via bus  110  to network port  112 , fiber port  114  and memory  116 . Processor  108  can be, for example, an Intel Pentium® 4 processor, manufactured by Intel Corp. of Santa Clara, Calif. As another example, processor  108  can be an Application Specific Integrated Circuit (ASIC). An example of bus  110  is a peripheral component interconnect (“PCI”) local bus, which is a high performance bus for interconnecting chips (e.g., motherboard chips, mainboard chips, etc.), expansion boards, processor/memory subsystems, and so on. 
   Network port  112  can be an Ethernet port, a serial port, a parallel port, a Universal Serial Bus (“USB”) port, an Institute of Electrical and Electronics Engineers, Inc. (“IEEE”)  1394  port, a Small Computer Systems Interface (“SCSI”) port, a Personal Computer Memory Card International Association (“PCMCIA”) port, and so on. Memory  116  of client computer  102  can store a plurality of instructions configured to be executed by processor  108 . Memory  116  may be a random access memory (RAM), a dynamic RAM (DRAM), a static RAM (SRAM), a volatile memory, a non-volatile memory, a flash RAM, polymer ferroelectric RAM, Ovonics Unified Memory, magnetic RAM, a cache memory, a hard disk drive, a magnetic storage device, an optical storage device, a magneto-optical storage device, or a combination thereof. 
   Client computer  102  can be coupled to server computer  104  via network  106 . Server  104  can be, for example, a Windows NT server from Hewlett-Packard Company of Palo Alto, Calif., a UNIX server from Sun Microsystems, Inc. of Palo Alto, Calif., and so on. Server  104  can include a processor  118  coupled via bus  120  to network port  122 , fiber port  124  and memory  126 . Examples of network port  122  include a Wide Area Network (WAN), a Local Area Network (LAN), the Internet, a wireless network, a wired network, a connection-oriented network, a packet network, an Internet Protocol (IP) network, or a combination thereof. 
   As used to describe embodiments of the present invention, the terms “coupled” or “connected” encompass a direct connection, an indirect connection, or any combination thereof. Similarly, two devices that are coupled can engage in direct communications, in indirect communications, or any combination thereof. Moreover, two devices that are coupled need not be in continuous communication, but can be in communication typically, periodically, intermittently, sporadically, occasionally, and so on. Further, the term “communication” is not limited to direct communication, but also includes indirect communication. 
   Embodiments of the present invention relate to data communications via one or more networks. The data communications can be carried by one or more communications channels of the one or more networks. A network can include wired communication links (e.g., coaxial cable, copper wires, optical fibers, a combination thereof, and so on), wireless communication links (e.g., satellite communication links, terrestrial wireless communication links, satellite-to-terrestrial communication links, a combination thereof, and so on), or a combination thereof. A communications link can include one or more communications channels, where a communications channel carries communications. For example, a communications link can include multiplexed communications channels, such as time division multiplexing (“TDM”) channels, frequency division multiplexing (“FDM”) channels, code division multiplexing (“CDM”) channels, wave division multiplexing (“WDM”) channels, a combination thereof, and so on. 
   In accordance with an embodiment of the present invention, instructions configured to be executed by a processor to perform a method are stored on a computer-readable medium. The computer-readable medium can be a device that stores digital information. For example, a computer-readable medium includes a compact disc read-only memory (CD-ROM) as is known in the art for storing software. The computer-readable medium is accessed by a processor suitable for executing instructions configured to be executed. The terms “instructions configured to be executed” and “instructions to be executed” are meant to encompass any instructions that are ready to be executed in their present form (e.g., machine code) by a processor, or require further manipulation (e.g., compilation, decryption, or provided with an access code, etc.) to be ready to be executed by a processor. 
   Storage area network  100  includes a plurality of networked storage devices  128  accessible via fiber router  130 . Networked storage devices  128  may include, for example, one or more hard disk drives  132 ,  134 , and  136 , optical storage device  138 , removable storage device  140 , or other such storage devices. Fiber router  130  may be, for example, Chaparal FVS113, Crossroads 4250, ATTO Fiber Bridge 3200. Information stored on storage devices  128  may be accessible to client computer  102  and server computer  104  as if the devices were directly attached to the computers. For example, storage area on disk  132  may be “mounted” on server  104  and storage area on disk  134  may be mounted on client  102 . From the perspective of applications running on those computers, the storage areas will appear as if they are directly attached to the respective computer system. 
   In typical client-server environments, a client computer may need to read data stored on the server system or may need to write data to the server system. Conventional systems and methods for accomplishing such tasks have not been optimized to take advantage of storage area networks such as those shown in  FIG. 1 . For example, a conventional process for writing data from the client into a file on a server follow a communications flow shown in  FIG. 2 . In this examplen, client  102  has data stored on disk  132  that needs to be transferred for storage by server  104 . In  FIG. 2 , the transactions that are represented by solid lines consist of messages or data that is sent between the client and server computers. The dashed lines represent the actual interaction between client  102  and server  104  and networked storage devices  128  accessed via router  130 . 
   In step  201 , client  102  initiates a data write request by informing server  104  that the client has data to be written to a file maintained by server  104 . In step  202 , server  104  creates a new empty file on one of the networked storage devices  128 , such as hard disk  134 . In step  203 , server  104  sends a message to client  102  informing client  102  that a file has been created. In steps  204  and  205 , client  102  retrieves data from hard disk  132 . In step  206 , client  104  sends the data to server  104  with instructions to write the data to the new file. In step  207 , server  104  writes the data to the new file on hard disk  134 . In steps  208 – 215 , client  102  retrieves data and server  104  writes data as described until all of the data has been transferred from client  102  to server  104 . 
   This conventional method of data transfer does not result in an efficient file transfer between the two systems. Particularly, as shown in  FIG. 2 , the communications flow is not optimized because data that only needs to be moved from one physical location to another physical location within a single storage area network  100  is instead transferred out of the storage area network. Specifically, the data flows from storage area network  100  to client  102  via router  130 . Client  102  then transfers the data to server  104  via network  106 . Server  104  finally transfers the data back to storage area network  100  via router  130 . 
   Another inefficiency problem associated with conventional file transfer systems is that the server cannot optimize its storage of the data because it does not have enough information to manage the data transfer operation. This is applicable to storage area networks such as those shown in  FIG. 1 , as well as client-server systems wherein data is stored in locally-attached storage devices. Initially, the client requests that the server create a new, empty file. The server responds when it has done so. From that point onward, the client writes a subset of the file&#39;s total data in each of a sequence of write operations. The server may or may not acknowledge the receipt of the data, depending on the specifics of the protocol used. Similarly, when the client has written all the file&#39;s data to the file on the server, it may issue a final request or not, depending on the protocol used. 
     FIG. 3  illustrates the above-described inefficiency problem in more detail. In step, client  300  initiates a request to transfer data to server  301 . In step  303 , server  301  responds to the request by indicating that a new empty file has been created. In steps  304 – 305 , client  300  sends one or more data packets until the entire file has been transferred from client  300  to server  301 . Because server  301  does not have complete information about the data being transferred, the data is subsequently written to the new file in pieces of varying size. This may result in an inefficient utilization of available disk space. If multiple files are to be transferred, then steps  302 – 306  must be repeated, as shown in steps  307  and  308 . 
   The conventional method as described is widely used for populating the data space of a file, and is effective when the number and content of the data cannot be known in advance. However, because the server is only exposed to a subset of the total set of write data operations at any given time, the server&#39;s opportunities for optimization are limited. Particularly, the server cannot determine which available storage locations within a storage medium would best be suited for storage of the file, because the file&#39;s ultimate size is unknown. Further, the server cannot specify the order that the client should send the data, or, in cases where the client will ultimately send more than one file to the server, the sequence of the files. This deficiency is particularly pronounced in storage area networks, where it is typical for a client to transfer numerous files having particular contents and sizes known only to the client. In such environments, the transfer of file contents on a piecemeal basis results in a diminished data transfer rate. 
   Another serious limitation in utilizing the conventional methods of transferring data as illustrated in  FIGS. 2 and 3  arises when files are to be moved from a client to one or more removable-media devices on a server. In such systems, a server may manage a series of pieces of media, each of which has finite capacity. As data is placed on these media, each piece may have a different amount of space remaining. When these method are employed, and data is written in a piecemeal manner, a server may store a file&#39;s data on a piece of media where it will ultimately not fit. In such a situation, it may be necessary to later move the partially-written file to a new location so that further write operations may take place. 
   Accordingly, there is a need for a system and method for providing improved file transfer rates and efficient data placement on a data storage medium. 
   The general process for transferring data between client and server systems, described above, is also used in common network file sharing protocols, such as Network File Systems (NFS) and Common Internet File System (CIFS), wherein a client computer creates an empty file on a server, then writes data piecemeal to the file via the server. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to improve the data transfer rate between a client and a server in a computer network. 
   It is another object of the invention to improve the use of a third party copy feature of storage networks wherein the client and server exchange information regarding a set of data blocks to be transferred and delegate the transfer to a third party, thereby improving the data transfer rate and relieving the server and client load. 
   A further object is to reduce the number of steps needed to move files from a client to one or more removable media devices on a server. 
   Another object is to improve the utilization of removable media. 
   These objects, and others which will become apparent from the following disclosure are achieved by the present invention which in one aspect comprises a method and system for writing file data from client to server which comprises issuing by the client to the server a file transfer proposal which comprises the names of a plurality of files and attributes of each of the plurality of files, determining by the server optimum memory locations for the plurality of files and optimum sequence and size of data transfer, issuing by the server to the client a request to transfer the plurality of files in a sequence which is optimized for memory location and minimal number of data transfers, thereby maximizing data transfer rate from the client to the server. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a conventional architecture in which the present invention may be implemented to improve file transfers between client and server systems using storage area network devices. 
       FIG. 2  is a timeline illustrating transactions between a client system, a server system, and a storage area network for writing data to a file according to conventional methods. 
       FIG. 3  is a timeline illustrating transactions between a client system and a server system for writing data to multiple files according to conventional methods. 
       FIG. 4  is a timeline illustrating transactions between a client system and a server system for writing data to multiple files according to an embodiment of the present invention. 
       FIG. 5  is a timeline illustrating transactions between a client system, a server system, and a storage area network for writing data to a file according to an embodiment of the present invention. 
       FIG. 6  is a timeline illustrating transactions between a client system, a server system, and a storage area network for writing data to a file according to another embodiment of the present invention. 
       FIG. 7  is a schematic diagram of an architecture in which the present invention may be implemented to improve file transfers between client/server systems utilizing storage devices networked according to an ISCSI architecture. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As described above, the problems associated with conventional file transfer methods stems from the fact that the transfer is initiated from the client. As a result, too little information is available to efficiently place the files in storage media managed by the server system. Another problem with conventional file transfer methods is that too little information is available to make proper use of the so-called “third-party copy” feature of storage area networks. In the third-party copy scenario, the client and server need to identify the data blocks to be transferred from one system to the other. This information must then be provided to a third party, which issues the corresponding storage are network I/O operations effect the movement data. In order to write data from the client to the server, the party initiating the third-party copy must be aware of the locations (block addresses) of data on both the client and server. When write operations are performed piecemeal, initiated by the client, the server has not yet had an opportunity to allocate space for the anticipated data. Accordingly, the third-party copy feature cannot be used. 
   According a first embodiment of the present invention, a new method for writing data to one or more files from a first computer to a second computer is disclosed whereby information describing the one or more files is first sent from the first computer system to the second computer system before the data is transferred. Based upon this information, the second computer system requests file data from the client in a manner optimized according to the second computer&#39;s needs. That is, the second computer may dictate the order, time, and the communication medium for completing the data transfer. As a result, the server is enabled to optimize the placement and transfer of data. 
     FIG. 4  illustrates a new method for transferring one or more files from one system to another according to an embodiment of the present invention. In  FIG. 4 , a user of client  400  desires to transfer three files to server  401 , designated File1, File2, and File3. The client proposal to transfer all three files is sent to the server, along with such attributes for each file as to best facilitate the transfer. These attributes may include, for example, the file length and the location on a network storage device of each of the data blocks that compose the file. In the example, server  401  processes the request to transfer these three files, and determines that an optimal performance could be obtained by transferring the files in the order of File2, followed by File1 and File3, respectively. The order that is determined will optimize the data transfer by reducing the disk head seeking. Accordingly, in step  403 , server  401  instructs client  400  to send the contents of File2. In step  404 , client  400  sends the contents as requested. In steps  405  and  406 , data for File1 is requested and sent, as shown in  FIG. 4 . Similarly, in steps  407  and  408 , data for File3 is requested and transferred. The file transfer request may include allocation data to further improve the file transfer process. Allocation data may be comprised of, for example, the addresses on a storage area network device to which the data are to be transferred, at maximum data transfer rate. Allocating data may also include a scatter gather list of the block as they are allocated on the disk. 
   A first improvement resulting from the invention is an ability of the second computer, which in this example is server  401 , to prepare for a transfer size of its choosing. Using conventional methods, the first computer, in this case, client  400 , must assume that the other computer can accept a data transfer of a particular size. The need to make this assumption typically means that the sending system must make a conservative choice so as not to exhaust memory resources on the recipient system. In contrast, using methods of the present invention, the recipient system receives, in advance, the size of the data to be transferred (because of the file attributes sent by client  400 ), an so server  401  can prepare for as large a transfer as possible and inform the sending system (via the allocation data). In this way, it is possible to affect the transfer of a single file with a minimum number of data transfers and without exhausting the resources of the server. This maximizes the data transfer rate from client to server within the server&#39;s resource constraints. 
   A second improvement accomplished by the invention results because the server controls the sequence of files to be transferred. In removable media systems, such as those involving storage libraries, it is typical to optimize performance by placing particular files on particular pieces of media. Further, it is often the case that at any particular time, some pieces of media can be accessed more quickly than others. Continuing the example of  FIG. 4 , at the time that the transfer of File1, File2, and File3 is requested, it may be that the piece of media that is to hold File2 can be accessed most quickly. In this case, it would be advantageous to transfer File2 before either of the other files. The method embodied by the invention renders this possible by presenting all choices to the server at once and allowing it to determine the sequence that optimizes performance. 
   A third improvement results because the client and server can exchange information needed to perform third-party copy operations. Such operations are widely recognized for performance optimization because a data transfer can take place through a third-party agent without expending any resources by either client or server in the data transfer.  FIGS. 5 and 6  illustrate how the present invention facilitates third-party copy operations. As shown in  FIGS. 5 and 6 , the present invention provides for a significantly simplified interaction between the client, server, and storage area network. According to the present invention, data need not be transferred out of storage area network  100  to complete the file transfer. Instead, router  130  is instructed to carry out the file transfer operation within the storage area network. 
     FIG. 5  illustrates the interaction between client  102 , server  104 , and storage devices  128  according to an embodiment of the present invention to perform third party copy operations. In this embodiment, no acknowledgment messages are passed between the systems. In step  501 , client  102  sends a message to server  104  to initiate a file transfer. The initial message includes attributes of the file that is to be transferred, which is also referred to herein as “the source file.” As described above, attributes may include information such as the size and location of the source file. In this embodiment, the location of the source file further includes identification of actual data sectors on the storage medium indicating every component of data comprising the file. This information is commonly referred to in the art as “scatter-gather” data because it identifies the physical locations in which data is scattered across the storage medium and is needed to retrieve the data. The information is sent to the client in a copy request, and is stored in the request packet. 
   In step  502 , server  104  instructs router  130  to create a new empty file and to carry-out the data transfer from the source file to the new empty file, which then becomes the destination file. A message created in step  502  includes one or more of the file attributes received from client  102 . In step  503 , router  130  transfers the data from the source location to the destination location. That is, router  130  retrieves data from the sectors identified in the scatter-gather list and places them in available sectors on the destination storage medium. The sectors making up the new file are included in the destination file&#39;s header block for future reference as scatter-gather data. 
     FIG. 6  shows another example implementing the present invention to facilitate third-party transfers of data. This example includes all of the steps shown in  FIG. 5 , in additional steps  601 – 603 . In step  601 , server  104  sends a confirmation message back to client  102 . The confirmation informs client  102  that the new file has been created. In step  602 , which is performed after the data transfer has been completed by router  130 , router  130  sends a message to server  104 . Message  602  informs server  104  that the data transfer has been successfully completed. In step  603 , server  104  informs client  102  of the successful completion of the data transfer. 
   The foregoing disclosure of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
   Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.