On May 5, 2008, at 7:33 PM, Craig James wrote:
I had the opportunity to do more testing on another new server to see whether the kernel's I/O scheduling makes any difference. Conclusion: On a battery-backed RAID 10 system, the kernel's I/O scheduling algorithm has no effect. This makes sense, since a battery-backed cache will supercede any I/O rescheduling that the kernel tries to do.
this goes against my real world experience here.
pgbench -i -s 20 -U test pgbench -c 10 -t 50000 -v -U test
You should use a sample size of 2x ram to get a more realistic number, or try out my pgiosim tool on pgfoundry which "sort of" simulates an index scan. I posted numbers from that a month or two ago here.
-- Jeff Trout <jeff@xxxxxxxxxxxxx> http://www.stuarthamm.net/ http://www.dellsmartexitin.com/
