Hi all, We are tuning a PostgreSQL box with AIX 5.3 and got stucked in a very odd situation. When a query got ran for the second time, the system seems to deliver the results to slow. HereÂs some background info: AIX Box: PostgreSQL 8.4.4, AIX 5.3-9 64bits, SAN IBM DS3400, 8x450GB SAS 15K Raid-5 8GB RAM, 2.3GB Shared buffers Debian Box: PostgreSQL 8.4.4, Debian 4.3.2 64bits, SAN IBM DS3400, 5x300GB SAS 15K Raid-0 7GB RAM, 2.1GB Shared buffers Right now, we changed lots of AIX tunables to increase disk and SO performance. Of course, postgres got tunned as well. I can post all changes made until now if needed. To keep it simple, I will try to explain only the buffer read issue. This query [1] took like 14s to run at AIX, and almost the same time at Debian. The issue is when I run it for the second time: AIX - 8s Debian - 0.3s These times keep repeating after the second run, and I can ensure AIX isnÂt touching the disks anymore. IÂve never seen this behaviour before. I heard about Direct I/O and I was thinking about givng it a shot. Any ideas? 1 - http://explain.depesz.com/s/5oz []Âs, Andrà Volpato -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
