Re: Load Distributed Checkpoints test results
От | PFC |
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Тема | Re: Load Distributed Checkpoints test results |
Дата | |
Msg-id | op.ttzc47iicigqcu@apollo13 обсуждение исходный текст |
Ответ на | Re: Load Distributed Checkpoints test results ("Gregory Maxwell" <gmaxwell@gmail.com>) |
Список | pgsql-hackers |
On Fri, 15 Jun 2007 22:28:34 +0200, Gregory Maxwell <gmaxwell@gmail.com> wrote: > On 6/15/07, Gregory Stark <stark@enterprisedb.com> 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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