On Fri, 15 Jun 2007 22:28:34 +0200, Gregory Maxwell <[EMAIL PROTECTED]> wrote:

On 6/15/07, Gregory Stark <[EMAIL PROTECTED]> wrote:
While in theory spreading out the writes could have a detrimental effect I
think we should wait until we see actual numbers. I have a pretty strong
suspicion that the effect would be pretty minimal. We're still doing the same
amount of i/o total, just with a slightly less chance for the elevator
algorithm to optimize the pattern.

..and the sort patching suggests that the OS's elevator isn't doing a
great job for large flushes in any case. I wouldn't be shocked to see
load distributed checkpoints cause an unconditional improvement since
they may do better at avoiding the huge burst behavior that is
overrunning the OS elevator in any case.

...also consider that if someone uses RAID5, sorting the writes may produce more full-stripe writes, which don't need the read-then-write RAID5 performance killer...

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