Electrical computers and digital data processing systems: input/ – Input/output data processing – Peripheral adapting
Reexamination Certificate
2000-11-10
2004-02-24
Gaffin, Jeffrey (Department: 2182)
Electrical computers and digital data processing systems: input/
Input/output data processing
Peripheral adapting
C710S001000, C710S005000, C710S007000, C710S020000, C710S062000, C710S064000, C710S065000, C710S072000, C710S305000, C709S241000, C709S241000, C709S200000, C709S213000, C709S217000, C709S218000, C709S225000, C709S227000, C709S246000
Reexamination Certificate
active
06697895
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer systems and, in particular, to the communication of information between a host computer and a remotely located tape storage device.
BACKGROUND OF THE INVENTION
Presently, a basic computer system includes: (1) a processor for executing instructions; (2) a memory for containing the instructions executed by the processor and, in many cases, the result of an instruction that has been executed by the processor; (3) an input peripheral, such as a keyboard or mouse; (4) an output peripheral, such as a monitor or printer; and (5) a storage peripheral, such as a tape or disk drive that provides storage beyond that provided by the memory. When a computer system is in operation, the memory contains at least one program, i.e., a list of instructions that are executed by the processor to accomplish one or more tasks. Typically, the memory contains all or part of a program that is known as an operating system and all or part of an application program. The operating system is a program that performs certain basic tasks, like processing input from a keyboard, sending output to a monitor, keeping track of files and directories, and controlling any storage peripherals that are part of the system. An application program is a program that is designed to perform a particular task or tasks for a user, such as word processing. Typically, the execution of an application program requires communication with an input peripheral, output peripheral, storage peripheral, a particular file etc. To achieve such communications, the application program utilizes the operating system. For instance, if an application program required a particular data file to perform a particular task, the application program would issue a request for the file to the operating system. In turn, the operating system would determine where the data file is located (e.g., a disk drive) and issue the appropriate command(s) to retrieve all or part of the file and place the file in the memory such that the file can be used by the application program.
Presently, peripherals such as disk and tape drives are commonly attached to the rest of a computer system via a Small Computer System Interface (SCSI). Peripherals that are attached via a SCSI interface are considered “local” peripherals. Further, many application programs are written so as to utilize “local” peripherals.
In many work environments, computer systems are linked together to form computer networks that allow the member computer systems to share information with one another. There are many different types of computer networks. For instance, there are local-area networks (LANs) in which the member computer systems are geographically close to one another, such as in the same building. There are also wide-area networks (WANs) in which the member computer systems are separated from one another by distances that require the use of telephone, optical and/or radio communication systems to link the computer systems to one another. Computer networks are also characterized according to: (1) topology, i.e., the geometric arrangement of the member computer systems and the interconnections between the systems; (2) protocol, i.e., the set of rules and signals that are used by the member computer systems to communicate with one another; and (3) architecture, which can be broadly classified as either: (a) peer-to-peer in which member computer systems have substantially the same capabilities; or (b) client/server in which “client” computer systems execute application programs that typically require the resources managed by the “server” computer systems, such as files and directories.
SUMMARY OF THE INVENTION
The present invention allows application programs that are executing on a particular computer system and that have been designed to utilize a “local” SCSI tape storage devices(e.g., tape drives and tape libraries) associated with the computer system to access SCSI tape storage devices that are remotely located, i.e., associated with another computer system in a computer network.
In one embodiment, a host computer system and SCSI tape storage device that is remotely located relative to the host computer are connected to one another via a computer network, e.g., a LAN or WAN. Incorporated into the host computer system is a virtual adapter that interfaces with the operating system of the host computer such that from the operating system perspective, the operating system sends /receives SCSI command related information to/from a local SCSI tape storage device, i.e., a SCSI tape storage device associated with the host computer system. However, the virtual adapter actually enables communication of the SCSI command related information with the remotely located SCSI tape storage device by appropriate encoding and decoding of the SCSI command related information. Specifically, the virtual adapter: (1) receives unencoded SCSI command related information (i.e., normal SCSI command related information) from the host computer operating system; (2) encodes the unencoded SCSI command related information received from the operating system so that the information is in a suitable format for transmission via the computer network to a SCSI tape storage device that is associated with another computer system in the network, i.e., a remote SCSI tape storage device; (3) decodes encoded SCSI command related information received over the computer network from a remotely located SCSI tape storage device; and (4) transmits the decoded SCSI command related information to the host operating system, which can then convey the information, if needed, to the application program.
The remotely located SCSI tape storage device includes a controller that: (1) decodes the encoded SCSI command related information received from the network so that the SCSI command related information can be applied to an actual SCSI tape storage unit; and (2) encodes the unencoded SCSI command related information produced by the SCSI tape storage unit for transmission over the network to the host computer system.
In one embodiment, it has been recognized that the operating system must initially identify all the local SCSI devices associated with the host computer but that it is not possible to identify a remote SCSI device that the host computer communicates with via the virtual adapter at the point in time because the operating system has not yet reached the point in the “boot up” process at which network communications are enabled. To address this problem, a program is provided that allows a user of the host computer system to identify the remote SCSI tape storage devices associated with the virtual adapter and store the information that the operating system would require from these devices during boot up of the host computer in a location that is accessible to the host computer. In one embodiment, the information is stored in the system registry, a portion of the host computer memory that is dedicated to the operating system. In this embodiment, when the host computer is being booted up, the operating system loads the virtual adapter and then sends an inquiry command to the virtual adapter to identify the SCSI devices associated with the adapter. In response, the virtual adapter provides the operating system with the information stored in the registry that relates to the remote SCSI tape storage devices, which are meant to appear to the operating system as local SCSI tape storage devices.
In another embodiment, the number of exchanges between the host computer and the remote SCSI tape storage device to process a SCSI command is reduced. The typical sequence of communications between a host computer and a SCSI device in processing a SCSI command is: (1) the host computer sends a command to a SCSI device; (2) the SCSI device accepts the command and sends a “request for data” to the host computer; (3) the host computer sends the data to the SCSI device; and (4) the SCSI sends a response to the host computer concerning the processing of the command and related data. As a consequence,
Nemeth Joe C.
Sayed Husni S.
Sherritt Jay
Starr Matthew T.
Gaffin Jeffrey
Holland & Hart LLP
Kulish, Esq. Christopher J.
Nguyen Tanh Q.
Spectra Logic Corporation
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