Alex Dean wrote:
> On Oct 1, 2010, at 11:01 AM, Eric Shubert wrote:
> 
>> Alex Dean wrote:
>>> On Oct 1, 2010, at 3:32 AM, der.hans wrote:
>>>> Am 30. Sep, 2010 schwätzte Eric Shubert so:
>>>>
>>>>> Which elevator is being used?
>>>>> (cat /sys/block/sda/queue/scheduler)
>>>> noop anticipatory deadline [cfq]
>>>>
>>>>> Using async i/o? Synchronous writes are very slow.
>>>> Hmm, not familiar with libaio. Looks like we have it installed.
>>>>
>>>>> I presume ext3, since you referred to noatime. If you have directories with many files (e.g. Maildir), dir_index option can help.
>>>> Yeah, ext3. Mostly it's a few DB files and some log files. No mail
>>>> directories.
>>> FWIW: A few years ago, I recall seeing somewhat-improved benchmark performance from MySQL after switching to the deadline scheduler.
>> I'd give that a shot - can't hurt to try.
>> # echo deadline >/sys/block/sda/queue/scheduler
> 
> I thought it required a reboot to change scheduler.  Maybe that's changed in more recent kernels.  (This was RHEL4, so 2.6.9-something.)
> 
> alex

You need to include the elevator= kernel parameter to make the change 
persist. You can use different schedulers for different devices by 
including the echo command in the /etc/rc.local file (overriding the 
elevator parameter, per device).

-- 
-Eric 'shubes'

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