Seagate Medalist 2160N (ST52160N), Product Manual

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Number of segments Size of segment (in Kbytes)
1 96
2 48
4 24
When the buffer is divided into multiple segments, each segment func-
tions as an independent buffer, causing dramatically increased perform-
ance in multitasking and multiuser environments at the expense of poorer
performance commands with long transfer lengths.
C.6.2 Write caching and write merging
Write caching. The drive uses a segment to store Write data. After the
drive receives the data from the initiator and caches the data, the
command is terminated and the drive is ready to process new com-
mands. The drive writes data to the disc before processing any nonwrite
command.
Write merging. Write merging uses the Write Immediate function. Write
Immediate terminates the command as soon as the initiator data is sent.
Write Immediate can be performed on an isolated write command. If
Write Immediate is used on write commands that are close enough in
time that the initiator data is present from the subsequent command
before the original command’s data is completely written to disc, then the
two write commands can be merged. The problem with this option is that
status is sent before the data is written to the disc. For disc errors, SCSI
has a function called Deferred Error reporting; the next command sent
receives a CHECK CONDITION status, and the SENSE data reports a
deferred error for the Write that had the error. The command that had the
CHECK CONDITION status may not be related to the Write error.
Medalist Pro 2160N/2160WC Product Manual, Rev. A 109