On Aug 17, 2011, at 1:56 PM, Tomas Vondra wrote: > On 17 Srpen 2011, 18:39, Ogden wrote: >>> Yes, but it greatly depends on the amount of WAL and your workload. If >>> you >>> need to write a lot of WAL data (e.g. during bulk loading), this may >>> significantly improve performance. It may also help when you have a >>> write-heavy workload (a lot of clients updating records, background >>> writer >>> etc.) as that usually means a lot of seeking (while WAL is written >>> sequentially). >> >> The database is about 200Gb so using /usr/local/pgsql/pg_xlog on a virtual >> disk with 100Gb should not be a problem with the disk space should it? > > I think you've mentioned the database is on 6 drives, while the other > volume is on 2 drives, right? That makes the OS drive about 3x slower > (just a rough estimate). But if the database drive is used heavily, it > might help to move the xlog directory to the OS disk. See how is the db > volume utilized and if it's fully utilized, try to move the xlog > directory. > > The only way to find out is to actualy try it with your workload. Thank you for your help. I just wanted to ask then, for now I should also put the xlog directory in the /var/lib/pgsql directory which is on the RAID container that is over 6 drives. You see, I wanted to put it on the container with the 2 drives because just the OS is installed on it and has the space (about 100Gb free). But you don't think it will be a problem to put the xlog directory along with everything else on /var/lib/pgsql/data? I had seen someone suggesting separating it for their setup and it sounded like a good idea so I thought why not, but in retrospect and what you are saying with the OS drives being 3x slower, it may be okay just to put them on the 6 drives. Thoughts? Thank you once again for your tremendous help Ogden -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
