On Sun, Mar 20, 2011 at 5:31 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Sat, Mar 19, 2011 at 11:34 AM, Grzegorz Jaskiewicz > <g...@pointblue.com.pl> wrote: >> >> On 18 Mar 2011, at 21:12, Robert Haas wrote: >> >>> While investigating Simon's complaint about my patch of a few days >>> ago, I discovered that synchronous replication appears to slow to a >>> crawl if fsync is turned off on the standby. >>> >>> I'm not sure why this is happening or what the right behavior is in >>> this case, but I think some kind of adjustment is needed because the >>> current behavior is quite surprising. >> We have few servers here running 8.3. And few weeks ago I had to populate >> one database with quite a number of entries. >> I have script that does that, but it takes a while. I decided to turn fsck >> to off. Oddly enough, the server started to crawl quite badly, load was very >> high. >> That was 8.3 on rhel 5.4. >> >> My point is, it is sometimes bad combination of disks and controllers that >> does that. Not necessarily software. fsync off doesn't always mean that >> things are going to fly, it can cause it to expose hardware bottlenecks much >> quicker. > > Well, it's possible. But I think it'd be worth a look at the code to > see if there's some bad interaction there between the no-fsync code > and the sync-rep code - like, if we don't actually fsync, does the > flush pointer ever get updated?
No, as far as I read the code. Disabling fsync increases the time taken to close the WAL file? Regards, -- Fujii Masao NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
