Hi Andy, No, I don't shrink the database. I simply purge the whole thing and then let it populate again. The data isn't too critical. The disks I have are internal SAS disks. I get around 150MB/sec write and 250MB/sec read. Its a RAID1 . ps does show idle in transactions. I've never checked pg_locks. How would I do that ? On Sun, Jan 16, 2011 at 12:28 PM, Andy Colson <andy@xxxxxxxxxxxxxxx> wrote: > On 01/16/2011 10:44 AM, Mag Gam wrote: >> >> I am running Redhat 5.2 Linux with Postgresql 8.4.4; >> >> When my disk space is 90% free the database performance is very good. >> However, when it reaches close to 20% free the database performance is >> bad. I know its bad because I see a lot of 'D' next to 'postgresql' >> process when running top and I see a lot 'WAITING' in the 'ps' tree. I >> was wondering if there are any filesystem tweaks I can do to make >> postgresql run smoother. I am currently using ext3. Should I consider >> using a different file system for my database? >> > > I doubt its a disk space problem. ÂSounds like a cache/disk io problem. > ÂWhen you are using 80% space, do you do something to get it back to 90% > free (ie shrink the db)? > > When the db is small, it fits in ram, and read's will be very quick. ÂOnce > your db gets bigger than cache it'll have to start using a lot more disk io. > > What kind of disk IO throughput do yo have? ÂWhat kind of disk system is > this? (raid, scsi, etc) > Does ps ever show 'idle in transaction'? > Have you checked pg_locks to see what you are waiting on? > Have you watched vmstat while its at 80% full vs when its at 80% free? > Â(does the iowait go up?) > > > -Andy > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
