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