On Mon, 2007-11-26 at 17:00 -0600, Scott Marlowe wrote: > On Nov 26, 2007 4:50 PM, Damon Hart <dhcom@xxxxxxxxxxx> wrote: > > > > So, what's different between these tests? I'm seeing performance > > differences of between +65% to +90% transactions per second of the > > OpenVZ kernel running on the HN over the stock Fedora 8 kernel. Is > > this reflective of different emphasis between RHEL and Fedora kernel > > builds? Some OpenVZ optimization on top of the RHEL5 build? Something > > else? Where should I look? > > > > any insights much appreciated, > > How many TPS are you seeing on each one? If you are running 10krpm > drives and seeing more than 166.66 transactions per second, then your > drives are likely lying to you and not actually fsyncing, and it could > be that fsync() on IDE / SATA has been implemented in later kernels > and it isn't lying. > > Hard to say for sure. > > What does vmstat 1 have to say on each system when it's under load? I will have to repeat the tests to give you any vmstat info, but perhaps a little more raw input might be useful. Test H/W: Dell Precision 650 Dual Intel CPU: Dual XEON 2.4GHz 512k Cache RAM: 4GB of DDR ECC Hard Drive: 4 x 36GB 10K 68Pin SCSI Hard Drive pgbench scale: 50 clients: 50 transactions per client: 100 stats for 30 runs each kernel in TPS (excluding connections establishing) OpenVZ (RHEL5 derived 2.6.18 series) average: 446 maximum: 593 minimum: 95 stdev: 151 median: 507 stock Fedora 8 (2.6.23 series) average: 270 maximum: 526 minimum: 83 stdev: 112 median: 268 Does your 10K RPM drive 166 TPS ceiling apply in this arrangement with multiple disks (the PostgreSQL volume spans three drives, segregated from the OS) and multiple pgbench clients? I'm fuzzy on whether these factors even enter into that rule of thumb. At least as far as the PostgreSQL configuration is concerned, fsync has not been changed from the default. Damon ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
