Doug, > Many disks implement the SCSI PRE-FETCH commands. One use case might > be a disk-to-disk compare, say between disks A and B. Then this > sequence of commands might be used: PRE-FETCH(from B, IMMED), > READ(from A), VERIFY (BYTCHK=1 on B with data returned from READ). The > PRE-FETCH (which returns quickly due to the IMMED) fetches the data > from the media into B's cache which should speed the trailing VERIFY > command. The next chunk of the compare might be done in parallel, > with A and B reversed. Minor nit: I agree with the code and the use case. But the commit description should reflect what the code actually does (not much in the absence of cache, etc.) -- Martin K. Petersen Oracle Linux Engineering
