On 19/02/13 13:39, Josh Berkus wrote:
Scott,
So do you have generally slow IO, or is it fsync behavior etc?
All tests except pgBench show this system as superfast. Bonnie++ and DD
tests are good (200 to 300mb/s), and test_fsync shows 14K/second.
Basically it has no issues until checkpoint kicks in, at which time the
entire system basically halts for the duration of the checkpoint.
For that matter, if I run a pgbench and halt it just before checkpoint
kicks in, I get around 12000TPS, which is what I'd expect on this system.
At this point, we've tried 3.2.0.26, 3.2.0.27, 3.4.0, and tried updating
the RAID driver, and changing the IO scheduler. Nothing seems to affect
the behavior. Testing using Ext4 (instead of XFS) next.
Might be worth looking at your vm.dirty_ratio, vm.dirty_background_ratio
and friends settings. We managed to choke up a system with 16x SSD by
leaving them at their defaults...
Cheers
Mark
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