Optical disk system emulating magnetic tape units

Filing Information

• Patent Number: US5438674
• Application Number: US8270109
• Filing date: 07/01/1994
• Issue date: 08/01/1995
• Predicted expiration date: 04/05/2008

• U.S. Classifications: 395/404  · 395/500  ·
• International Classifications: G06F 500 ·
• International Classifications: 364DIG. 1;DIG. 2 ·
• Related U.S. Application Data:
  This is a continuation of application Ser. No. 07/678,547 filed Mar. 28, 1992, now abandoned, which application is itself a continuation of application Ser. No. 07/177,491, filed Apr. 5, 1988, now abandoned.
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Patent Family

Abstract

An optical disk system emulating a 3480 magnetic tape subsystem having one or more magnetic tape drives, includes a VMEGate channel attached processor for receiving CCW tape commands, a SCSI board for controlling SCSI optical disk drives, a serial I/O board for controlling jukebox optical disk media handlers for automatically robotically loading and unloading optical disks containing virtual tape data into the optical disk drives, a cache RAM for buffering data between the channel and the optical disk drives, operator consoles for emulating the 3480 magnetic tape subsystem control panels, an SBC computer and VME bus for central control of the system, and floppy and hard disk drives for storing emulation SBC programs and disk directories, to enable the system to exhibit an organization of virtual tape data into a system of pointers and user records of the virtual tapes, a reallocatable mapping between magnetic tape drives and the optical disk drives, disk directories cross referencing virtual tapes VSNs to optical disks for locating particular optical disks storing requested VSNs, and to enable WORM optical media to appear to the channel as rewritable magnetic tape through the conversion of tape commands to jukebox load operations and optical disk drive seek operations for increased performance, said system emulates a 3480 magnetic tape subsystem by using jukeboxes to automatically load optical media into and out of optical disk drives and by using a dynamic re-allocation method for maintaining a one-to-one mapping between the virtual magnetic tape drives and the optical disk drives, which reduces access speed to the data.

Independent Claims | See all claims (27)

1. 1. A system for emulating a magnetic tape subsystem having and controlling a plurality of magnetic tape drives so as to read to write magnetic tape data onto and from magnetic tapes, said magnetic tape subsystem connected to a channel communicating magnetic tape subsystem channel commands and magnetic tape data organized in channel data formats, said system being for the purposes of recording and reading virtual magnetic tape data on optical disks in response to said magnetic tape subsystem channel commands, said system comprising:an optical disk drive means responsive to optical disk drive commands, said optical disk drive means serving to record and to read said virtual magnetic tape data on said optical disks;a system memory means, connected to said channel and to said optical disk drive means and to a computer means,for buffering said virtual magnetic tape data bidirectionally between said computer means and said optical disk drive means,for buffering said magnetic data bidirectionally between said channel and said computer means, andfor storing computer programs; andcomputer means, connected between said channel and said optical disk drive means and connected to said system memory means,for executing said computer programs stored in said system memory means,for receiving said channel commands from said channel,for translating said channel commands into said optical disk drive commands,for transmitting said optical disk drive commands to said optical disk drive means,for receiving said magnetic tape data from said channel via buffering in said system memory means,for organizing said magnetic tape data into said virtual magnetic tape data,for transmitting said virtual magnetic tape data to said optical disk drive means via buffering in said system memory means,for receiving said virtual magnetic tape data from said optical disk drive means via buffering in said system memory means,for reorganizing said virtual magnetic tape data into said magnetic tape data, andfor transmitting said magnetic tape data to said channel via buffering in said system memory means;wherein said computer means communicates through said channel within said channel data formats;wherein said computer means accepts channel commands that are sufficient for said magnetic tape subsystem to control said plurality of magnetic tape drives to read and to write in order to, in response to said channel commands and instead of controlling said plurality of magnetic tape drives, control said optical disk drive means to read and to write; andwherein said optical disk drive means, said system memory means and said computer means, collectively emulate said magnetic tape subsystem.
2. 7. A system for emulating a magnetic tape subsystem connected to a plurality of magnetic tape drives serving to read and to write magnetic tape data onto and from a plurality of magnetic tapes, and connected to a channel communicating magnetic tape subsystem channel commands and said magnetic tape data within channel data formats, said emulation system being for the purpose of reading and writing virtual magnetic tape data on a plurality of optical disks, said system comprising:a plurality of optical disk drives for reading and for writing said virtual magnetic tape data on said plurality of optical disks, said plurality of optical disk drives being controlled for said reading and said writing by optical disk drive commands;a bus means for communicating said virtual magnetic tape data, said magnetic tape data, and said optical disk drive commands;a data buffer memory means, connected to said bus means and to said data buffer memory means, for buffering said magnetic tape data and said virtual magnetic tape data;an optical disk drive processor means, executing drive processor programs and connected between said bus means and said plurality of optical disk drives, for receiving and for processing optical disk drive processor commands, for communicating said virtual magnetic tape data between said data buffer memory means and said plurality of optical disk drives, and for transmitting said optical disk drive commands to said plurality of optical disk drives;a channel processor means, connected between said channel and said bus means and executing channel processor programs, for receiving and processing channel processor commands, for receiving said channel commands and for retransmitting said channel commands, and for communicating said magnetic tape data between said channel and said data buffer memory means;a computer program memory means storing computer programs and said optical disk drive commands; anda computer means,connected to said computer program memory means for executing said computer programs and for accessing said optical disk drive commands stored therein,connected to said channel processor means for transmitting said channel processor commands thereto and for receiving said channel commands re-transmitted therefrom,connected to said optical disk drive processor means for transmitting said optical disk drive processor commands thereto,programmed to translate said channel commands into said optical disk drive commands, said channel processor commands and said optical disk-drive processor commands,programmed to organize said magnetic tape data into said virtual magnetic tape data,programmed to reorganize said virtual magnetic tape data into said magnetic tape data,programmed to command said channel processor means to communicate said magnetic tape data between said channel and said data buffer memory means through said bus means, and to communicate said magnetic tape data through said channel within said channel data formats, andprogrammed to command said optical disk drive processor means to transmit said optical disk drive commands to said optical disk drive means and to transmit said virtual magnetic tape data between said data buffer memory means and said plurality of optical disk drives.
3. 14. A system for emulating a magnetic tape subsystem connected to a plurality of magnetic tape drives serving to read and to write magnetic tape data on a plurality of magnetic tapes, and connected to a host computer having a channel serving to communicate magnetic tape subsystem channel commands to said magnetic tape subsystem so as to direct the reading and writing of said magnetic tape data on said plurality of magnetic tapes, said channel communicating within channel data formats, said magnetic tape subsystem communicating said magnetic tape data between said channel and said plurality of magnetic tape drives, said channel commands having serial numbers identifying a one of said plurality of magnetic tapes and having channel addresses respectively identifying a one of said plurality of magnetic tape drives, said system being for the purpose of reading and of writing virtual magnetic tape data on a plurality of optical disks each of which records a plurality of virtual magnetic tapes, said system comprising,a plurality of optical disk drives each of which is allocated to a respective ones of said plurality of magnetic tape drives and each of which is controlled by optical disk drive commands for reading and writing said virtual magnetic tape data on respective ones of said plurality of optical disks;a bus for communicating said magnetic tape data, said virtual magnetic tape data, and said optical disk drive commands,a cache RAM, connected to said bus, for buffering said virtual magnetic tape data communicated to and from said plurality of optical disk drives, and for buffering said magnetic tape data communicated to and from said channel;a computer bus RAM connected to said bus for storing said optical disk drive commands;a disk drive processor, connected between said plurality of optical disk drives and said bus, for reading said optical disk drive commands from said computer bus RAM, for communicating said optical disk drive commands to said plurality of optical disk drives, and for communicating said virtual magnetic tape data between said plurality of optical disk drives and said cache RAM;a channel processor, connected between said channel and said bus, for receiving said channel commands through said channel and for communicating said magnetic tape data between said cache RAM memory and said channel;a computer program RAM for storing computer programs; anda computer connected to said computer program RAM for reading and executing said computer programs, and for, responsively to the executing,receiving said channel commands via said bus from said channel processor,assigning said channel addresses to said optical disk drives,generating from received said channel commands said optical disk drive commands suitable to command said optical disk drive processor,storing said optical disk drive commands in said computer bus RAM memory,organizing said magnetic tape data received through said channel into virtual magnetic tape data recorded on optical disks,reorganizing said virtual magnetic tape data into said magnetic tape data, andgenerating channel processor commands that are communicated to said channel processor via said bus in order to command said channel processor to communicate said magnetic tape data upon said channel via said bus.
4. 20. A method of reallocating at least one magnetic tape drive to at least one optical disk drive in a system for reading and writing with a plurality of optical disk drives a plurality of virtual magnetic tapes recorded on a plurality of optical disks, said system communicating within channel data formats as would a magnetic tape subsystem having a plurality of magnetic tape drives for reading and writing magnetic tape data on a plurality of magnetic tapes, said magnetic tape subsystem connected to a channel communicating magnetic tape subsystem channel commands and said magnetic tape data, said channel commands having a plurality of channel addresses for respectively addressing a plurality of magnetic tapes and magnetic tape drives, said system being connected to said channel and comprising a programmed computer with memory, said method comprising the steps of,assigning each of the plurality of optical disk drives each to a respective one of said plurality of channel addresses so as to therein allocate each of the plurality of magnetic tape drives to the plurality of optical disk drives,receiving one of said channel commands requesting the writing or reading of a particular one magnetic tape by such an addressed one of said plurality of magnetic tape drives as is identified by a respective channel address,determining which one of said plurality of optical disk drives is loaded with that one of said plurality of optical disks that stores said particular magnetic tape as one of said plurality of virtual magnetic tapes, andreassigning the determined one of said plurality of optical disk drives to another one of said plurality of channel addresses, therein to reallocate which one of the plurality of said optical disk drives is identified to said particular one magnetic tape drive.
5. 23. A method of accessing one of a multiplicity of virtual magnetic tapes recorded on a plurality of optical disks in and by a system for emulating a magnetic tape subsystem that isconnected to a plurality of magnetic tape drives for reading and writing magnetic tape data on a multiplicity of magnetic tapes,further connected to a channel of a host computer communicating magnetic tape subsystem channel commands to said magnetic tape subsystem for the reading and writing of said magnetic tape data on said multiplicity of magnetic tapes,wherein said channel communicates said channel commands and magnetic tape data between said host computer and said magnetic tape subsystem within channel data formats,wherein said magnetic tape subsystem communicates said magnetic tape data between said channel and said plurality of magnetic tape drives,wherein said channel commands have serial numbers respectively identifying individual ones of said multiplicity of magnetic tapes,wherein said channel commands have channel addresses respectively identifying individual ones of said plurality of magnetic tape drives,wherein within the system each of said plurality of optical disks is recording at least one virtual magnetic tape, said system comprising a programmed computer with memory and a plurality of optical disk drives for reading and writing said virtual magnetic tapes on said plurality of optical disks, said system being connected to said channel and communicating said magnetic tape data across said channel within said channel data formats, said method comprising the steps of:assigning said channel addresses to said plurality of optical disk drives so as to allocate said plurality of magnetic tape drives to said plurality of optical disk drives, andgenerating a disk directory cross referencing said plurality of optical disks to said multiplicity of magnetic tapes referenced as respective ones of said virtual magnetic tapes,receiving a channel command requesting the writing or reading of magnetic tape data on an addressed one of said multiplicity of magnetic tapes in an addressed one of said plurality of magnetic tape drives having a one of said channel addresses,determining which selected one of said plurality of optical disk drives is allocated to said addressed one of said plurality of magnetic tape drives, and is assigned to said channel address,determining which selected one of said multiplicity of optical disks is that optical disk storing said addressed one of said multiplicity of magnetic tapes in the form of a virtual magnetic tape, andreading or writing said virtual magnetic tape data on said selected one of said plurality of optical disks in and by said selected one of said plurality of optical disk drives.
6. 26. A system writing and reading data from an optical disc so as to emulate the reading and the writing of a plurality of magnetic tapes that are individually addressable and controllable in any intermixed sequence for the writing and the reading of data, the optical disc system emulating magnetic tapes comprising:a first means for recording, in respect of each and every magnetic tape as is individually addressable and controllable intermixed in order with all other magnetic tapes, a virtual magnetic tape on the optical disc, each virtual magnetic tape includingdata records, called user records, located in addressable locations upon the optical disk and containing data that is written and read to and from a particular magnetic tape, anda first set of pointers, called a tape map, to all the addressable locations as contain all the user records as constitute the particular magnetic tape, the tape map being itself located in an addressable location;a second means for recording, in respect of any one or ones of additions, deletions and alterations to any one or ones of the virtual magnetic tapes,all new and additional user records, anda new, updated, tape map containing pointers to, and only to, all the addressable locations as contain all the most current user records as constitute a most current revision of a particular magnetic tape,wherein, consonant with the write once read many operational principles of optical disc media, old and outdated user records and tape maps cannot be and are not erased, but, for any virtual magnetic tape, a one most recent single tape map will contain pointers to all most current user records as constitute a most current revision of the virtual magnetic tape;a third means for recording in a dedicated area of the optical disc a directory, called a tape directory, of all the virtual magnetic tapes stored on the optical disk, the tape directory containing a pointer to the most current tape maps of each and all virtual magnetic tapes; anda fourth means for recording seriatim upon the optical disk in the dedicated area an updated tape directory as and upon the occasion that any one or ones of virtual tapes are any one or ones of added, deleted and altered;wherein the most current data contents of each and any virtual magnetic tape may readily be located upon and read from the optical disk by first reading tape directories seriatim until a last such directory is read, and then proceeding, by reference to the pointers within this tape directory contained, to second reading a most current tape map for an individual virtual magnetic tape of interest, and then proceeding, by reference to the pointers within this tape map contained, to third reading any addressable locations as contain the most current data.