Re: Higher than expected disk write(2) latency

[Martin Sustrik <sustrik@fastmq.com>]

Hi Alan,

>> What we see is that AIO performs rather bad while we are still 
>> enqueueing more writes (it misses right position on the disk and has to 
>> do superfluous disk revolvings), however, once we stop enqueueing new 
>> write request, those already in the queue are processed swiftly.
> 
> Which disk scheduler are you using - some of the disk schedulers
> intentionally delay writes to try and get better block merging.

It's CFQ. Does it delay writes? And if so, what should we use instead?

Thanks.
Martin