LOCK UNLOCK CACHE, PRE-FETCH, and SEEK commands
Elliott, Robert (Server Storage)
elliott at hp.com
Wed Oct 8 14:44:13 PDT 2003
* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <elliott at hp.com>
Does anyone use these block commands (on block devices)?
LOCK UNLOCK CACHE - force specified blocks to be kept in cache
PRE-FETCH - read specified blocks into cache
SEEK - advance notification that an LBA will be accessed
I've asked around and haven't found anyone who implements
the first two. The third is rather meaningless.
I wonder if it would be appropriate to make these changes
in SCSI Block Commands - 2 (SBC-2):
a) obsolete LOCK UNLOCK CACHE (10) and PRE-FETCH (10).
b) remove LOCK UNLOCK CACHE (16) and PRE-FETCH (16). These are
the 8-byte LBA versions that were added into SBC-2. Since SBC-2
has not been published yet (and assuming nobody has implemented
them), we might be able to reclaim their opcodes for future use
rather than mark them obsolete.
c) obsolete SEEK (10). An 8-byte LBA version was never proposed.
MMC-4 has its own definition of SEEK (10) for the multimedia
device type - SBC's definition isn't necessary for multimedia.
SEEK(6) was defined in SCSI-2 but obsolete in [SCSI-3] SBC[-1].
Rob Elliott, elliott at hp.com
Hewlett-Packard Industry Standard Server Storage Advanced Technology
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