On Thu, 25 Aug 2005 09:10:37 +0200 Ulrich Wisser <[EMAIL PROTECTED]> wrote:
> Pentium 4 2.4GHz > Memory 4x DIMM DDR 1GB PC3200 400MHZ CAS3, KVR > Motherboard chipset 'I865G', two IDE channels on board > 2x SEAGATE BARRACUDA 7200.7 80GB 7200RPM ATA/100 > (software raid 1, system, swap, pg_xlog) > ADAPTEC SCSI RAID 2100S ULTRA160 32MB 1-CHANNEL > 2x SEAGATE CHEETAH 15K.3 73GB ULTRA320 68-PIN WIDE > (raid 1, /var/lib/pgsql) > > Database size on disc is 22GB. (without pg_xlog) > > Please find my postgresql.conf below. > > Putting pg_xlog on the IDE drives gave about 10% performance > improvement. Would faster disks give more performance? Faster as in RPM on your pg_xlog partition probably won't make much of a difference. However, if you can get a drive with better overall write performance then it would be a benefit. Another thing to consider on this setup is whether or not you're hitting swap often and/or logging to that same IDE RAID set. For optimal insertion benefit you want the heads of your disks to essentially be only used for pg_xlog. If you're having to jump around the disk in the following manner: write to pg_xlog read from swap write syslog data write to pg_xlog ... ... You probably aren't getting anywhere near the benefit you could. One thing you could easily try is to break your IDE RAID set and put OS/swap on one disk and pg_xlog on the other. > If one query contains so much data, that a full table scan is needed, > I do not care if it takes two minutes to answer. But all other > queries with less data (at the same time) still have to be fast. > > I can not stop users doing that kind of reporting. :( > > I need more speed in orders of magnitude. Will more disks / more > memory do that trick? More disk and more memory always helps out. Since you say these queries are mostly on not-often-used data I would lean toward more disks in your SCSI RAID-1 setup than maxing out available RAM based on the size of your database. --------------------------------- Frank Wiles <[EMAIL PROTECTED]> http://www.wiles.org --------------------------------- ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings