G - Physics – 11 – B
Patent
G - Physics
11
B
352/16, 354/230.
G11B 15/02 (2006.01) G06F 3/06 (2006.01) G11B 15/06 (2006.01) G11B 27/13 (2006.01)
Patent
CA 1273710
ABSTRACT OF THE DISCLOSURE A magnetic tape system including: a drive mechanism (1) having motors (10a, 10b) for driving a pair of reels on which is wound magnetic tape (16) having a beginning-of-tape mark (BOT) and an end-of-tape mark (EOT) and having a magnetic head (14); a drive control unit (2, 20, 21), for control- ing the drive mechanism based on given commands so as to write data on or read data from the magnetic tape, calculat- ing the running distance of the magnetic tape based on the diameters of the magnetic tape, and issuing an EWA signal indicating the approach of the end of the magnetic tape before detection of the end of tape mark; and a prefetch control unit, having a first memory which stores a plurality of write commands from the host system including write com- mands which are not accompanied with write data from the host system, a second memory which stores a plurality of write data, and the read data from the magnetic tape, for operating the drive mechanism based on write commands received in advance from the host system and stored in the first memory via the drive control unit, writing data on or reading data from the magnetic tape based on commands from the host system, and reporting the results to the host system. The prefetch control unit may reduce the prefetching of write commands stored In the first memory after the receipt of the first EWA signal. Preferably, the prefetchings of write commands may be reduced when a write command sent from the host system is received. After the prefetch control unit receives the first EWA signal, the number of prefetched write commands is limited, the final limit being determined by the recording density and the maximum block length of the write commands. The running distance of the magnetic tape may be calculated and prefetch control performed until the cal- culated value reaches a value corresponding to a second EWA position corresponding to a position before the end marker of the magnetic tape. When the value corresponding to the second EWA position is reached, an EOT signal is issued to the host system and prefetchings of write commands from the host system are no longer accepted.
513624
Ishiguro Masayuki
Ohwa Noboru
Fujitsu Limited
Mcfadden Fincham
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