Storage Technology Corporation

Terry R Gottehrer

William C Dodt

Charles Allen Milligan

Donald F McCarthy

Keith Gary Boyer

Robert D Thompson

Kenneth R Burns

Jerry L Donze

Brian G Cleveland

Ronald W Korngiebel

Michael R Stephens

Thomas H Gohl

Bernie R Marasco

In response to the mounting of a magnetic tape on the tape drive, the tape drive begins reading data from the tape into the preload buffer while concurrently signalling the data processor that the tape drive is instantaneously available to read/write data. The data processor can then begin the data transfer operation without incurring the delay occasion by media set up time. The data that is transferred from magnetic tape is stored in the preload buffer in anticipation of the data processor issuing a data read command. Upon receipt of the data read command, the tape drive reads the data out of the preload buffer to the data processor via the data channel while simultaneously reading data from the magnetic tape into the preload buffer.

System for reading and stopping reading data from magnetic tape into

The present invention discloses a method and apparatus for computing CRC codes for fixed length page buffers of user data where the user data arrives from a transmission device in variable length packets with the packet contents being out of sequential order. The received data is written to a storage device after being restored to the correct sequential order. The data packets are comprised of a header portion and a data portion. The transmission and compression methods commonly employed by the transmission device dictates that the header portion of each packet follows the data portion. The present invention computes a complete CRC code for the data stored in a page buffer in real time as the packets are received by using several registers for saving intermediate CRC codes and circuitry to combine partial CRC codes for those packet portions received out of order. Additional circuitry is provided which reorders the data packet portions received out of order back into sequential order as the data is stored in a page buffer memory in real time. Computing the CRC codes in real time permits the saving of costs associated with other approaches that significantly buffer the incoming packets to permit subsequent reordering and CRC computation. The present invention assures data integrity of data from the time it is received from the compression unit until the time it is sent to the storage device. In addition, the present inventions ability to compute the CRC codes real time maintains optimal performance of data throughput of the storage subsystem. The present invention alleviates problems relating to delaying new data packet transmissions as deferred CRC computations are performed on previous packets reordered in temporary buffer memory.

Apparatus and method for CRC computation over fixed length blocks

Control software and hardware in the tape drive control unit creates and manages a header segment at the beginning of the magnetic tape. This header segment includes an administrative information section that contains data relating to the magnetic tape itself. The administrative information includes read/write status information such as the write protect status of the magnetic tape that enables the tape drive control unit to manage the data records written onto the magnetic tape without reference to any other source of administrative data. In addition, each data record written on the magnetic tape includes a header which denotes the read/write status of the data record.

Method and apparatus for managing data on rewritable media to define

The control software and hardware in the tape drive control unit creates and manages a header segment at the beginning of the magnetic tape. This header is interposed between a leader portion of the magnetic tape on the 3480-type cartridge and the remainder of the magnetic tape contained therein. This header segment contains two sections, a first of which is a data record directory that is used by the control unit to denote the location of each data record written on to the magnetic tape as well as administrative information associated with the data record. The second section of the header is an administrative information section that contains data relating to the magnetic tape itself. The stream of data records is divided into data segments, a plurality of which comprise a single helical scan track. The helical scan tracks are formed into scan groups and written on the magnetic tape. At least one longitudinal track is written on the magnetic tape coextensive with the helical scan groups to provide data to enable the tape drive to quickly locate data records recorded on the magnetic tape.

Method and apparatus for recording data on magnetic tape media

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Louisville, CO, United States of America

Terry R Gottehrer