Data processing: structural design – modeling – simulation – and em – Emulation – Compatibility emulation
Reexamination Certificate
1998-12-22
2001-07-10
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Emulation
Compatibility emulation
C703S024000, C711S004000, C711S111000
Reexamination Certificate
active
06260006
ABSTRACT:
TECHNICAL FIELD
The present invention relates to servicing requests received by a magnetic tape library and library management resulting therefrom.
BACKGROUND ART
Digital magnetic tape is commonly used for long term storage in computer systems. The low cost per bit stored, long term retention capability, and portability of magnetic tape cartridges has made magnetic tape the medium of choice for storing the large quantities of data produced by businesses such as banks, credit card companies, airlines, and the like. Automated tape libraries are often used to rapidly handle the number of tape cassettes required to hold large amounts of data. Such automated tape libraries typically include multiple tape units for accessing data on magnetic tapes and a robotic tape handling system for transferring tape cartridges between a tape unit and a cartridge storage location.
The large amounts of data to be stored are typically broken into volumes by host computers that process the data. A single tape cartridge is then used to hold the data volume. This may lead to waste as the magnetic tape stored in the cartridge may be capable of holding significantly more data than is contained in the volume. Also, tape management is typically controlled by a host computer. The host computer tracks location of cartridges, the volume on each cartridge, and the cartridge or cartridges being accessed by each tape unit.
One difficulty with current tape management systems is the overhead required of the host computer to manage the tape library. Another difficulty is that the tape management system within the host computer must be modified each time changes are made to the tape library. Yet another problem of current tape management systems implemented in host computers is the inability to manage tape cassettes containing multiple volumes.
A further difficulty with previous tape management systems becomes apparent when data must be manually put into or taken out of the computer system. For example, consider bringing data into the computer system from a separate computer system. If the tape cartridge is compatible with tape units in the automated tape library, the new tape must be manually introduced into the robotic tape handling system. The host computer must then be instructed to assign the new tape a volume identifier and process the tape into the tape library. If the new tape has a format incompatible with any tape unit in the automated tape system, a new tape unit must be connected to an open channel from the host computer. The host computer must then be directed to copy the information from the new tape cartridge onto a blank tape within the automated tape handling system. This may require writing specialized code for the host computer to access the new tape unit, read in the data, reformat the data for a cartridge type contained within the automated library system, and store the data on a blank tape cartridge.
What is needed is a tape library system that removes tape management functions from the host computer. This tape library system should handle multi-volume tapes to increase storage efficiency. The host computer should be presented with a virtual view of tape volumes and tape units so that extensive reprogramming of the host computer is not required. The tape management system should also allow for convenient copying of data to and from tape cartridges external to the automated tape library.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a means for reducing tape management overhead required by a host computer.
Another object of the present invention is to provide support for handling multi-volume tape cartridges.
Still another object of the present invention is to provide a host computer with a virtual view of connection to a specified tape volume loaded in a specified tape unit.
Yet another object of the present invention is to provide convenient manual copying of data into and out of an automated tape library.
In carrying out the above objects and other objects and features of the present invention, a tape library system for handling multi-volume tapes is provided. The system includes an automated tape system with tape units for writing data to and reading data from magnetic tapes. The automated tape system also includes a robotic tape handling system for loading tape cartridges into and removing tape cartridges from the tape units. A tape/library control unit (TLCU) receives a request from a host computer to access a specified tape volume in a tape unit specified by the host computer. The TLCU maps the specified tape volume to a tape cartridge. A check is made to determine if the tape cartridge is currently loaded in a tape unit. If the tape cartridge is not loaded, the robotic tape handling system is commanded to load the tape cartridge into an available unit which may be different than the tape unit specified by the host computer. A virtual path is formed between the host computer and the loaded tape unit. Data is then transferred between the loaded tape unit and the host computer. This presents the host computer with a virtual view of connection to the specified tape volume loaded in the specified tape unit.
In an embodiment of the present invention, the TLCU can receive at least one write command from the host computer to write data to desired volume. If the tape cartridge containing the desired volume is loaded into a tape unit for access to a tape volume other than the desired tape volume, the write command is staged and the data is written in a storage system. When the tape cartridge containing the desired volume is no longer accessing a tape volume other than the desired tape volume, the staged write command is executed and the data from the storage system is written onto the tape cartridge. Similarly, the TLCU can receive a read command from the host computer to read data from a desired volume. If the tape cartridge containing the desired volume is loaded into a tape unit for access to a tape volume other than the desired tape volume, the read command is staged. When the tape cartridge containing the desired volume is no longer accessing a tape volume other than the desired tape volume, the staged read command is executed.
In another embodiment of the present invention, the tape library system includes at least one user accessible tape unit that is not part of the automated tape system. The TLCU can transfer data between an external tape cartridge loaded in the user accessible tape unit and a specified tape volume contained on a tape cartridge within the automated tape system without involvement by the host computer. In a refinement, the user accessible tape unit accepts tape cartridges having a format different than the tape cartridges used in the automated tape system.
In yet another embodiment of the present invention, the TLCU retains a list of volumes contained on each tape cartridge. The TLCU determines when the tape in each tape cartridge requires defragmenting based on the list of volumes. When a tape unit is available, the determined tape cartridge is loaded into the available tape unit and the tape is defragmented.
In a further embodiment of the present invention, the TLCU maintains an indication of usage for each tape unit. Determining into which tape unit a tape cartridge will be loaded is based on the usage indication for each tape unit, thereby balancing wear of tape units.
In a still further embodiment of the present invention, the TLCU provides tape volume management services including tape volume password creation and modification, tape volume expiration date creation and modification, tape volume ownership creation and modification, tape volume import, and tape volume export.
A method of servicing requests to a tape library system is also provided. The method includes receiving a request from a host computer to access a specified tape volume. The specified tape volume is mapped to a tape cartridge. If the tape cartridge is not currently loaded in a tape unit, the robotic tape handling system is commanded to load the tape cartridge into an
Noe Keith F.
Puckett Timothy L.
Wong Patrick K.
Brooks & Kushman P.C.
Frejd Russell W.
Storage Technology Corporation
Teska Kevin J.
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