Parallel Query Performance

From: Andy Marden <amarden_at_altavista.net>
Date: Fri, 27 Jul 2001 16:46:45 +0100
Message-ID: <k3g87.3954$Bp3.80305@news2-hme0>

Got a funny one here. We're running 8.1.7 on AIX 4.1.3 (RS6000s, 64 bit), 4 procs, 4Gb memory, LVM software striped RAID 0 disks (128Kb stripe width) over 12 disks. All this is for a Data Warehouse. Running some insert statements with queries shows large performance improvement for parallel 4 over single-threaded, not surprisingly, although we seem to see more than a 4x performance, which is a little wierd. What's strange, is that running 2 of these together dramatically worsens overall performance - actually making it worse than running them serially single-threaded. I would expect to see a slight degradation running them together, perhaps, if we were CPU or I/O bound, but I don't believe we should be. I/O wait is minimal.

Has anyone seen anything like this before?

Cheers

Andy Received on Fri Jul 27 2001 - 10:46:45 CDT