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? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
