On Thu, Jun 9, 2011 at 12:38 PM, Benjamin Franz <jfranz@xxxxxxxxxxx> wrote:
> On 06/09/2011 02:24 AM, Emmanuel Noobadmin wrote:
>> I'm trying to resolve an I/O problem on a CentOS 5.6 server. The
>> process basically scans through Maildirs, checking for space usage and
>> quota. Because there are hundred odd user folders and several 10s of
>> thousands of small files, this sends the I/O wait % way high. The
>> server hits a very high load level and stops responding to other
>> requests until the crawl is done.
>>
>> I am wondering if I add another disk and symlink the sub-directories
>> to that, would that free up the server to respond to other requests
>> despite the wait on that disk?
>>
>> Alternatively, if I mdraid mirror the existing disk, would md be smart
>> enough to read using the other disk while the first's tied up with the
>> first process?
> You should look at running your process using 'ionice -c3 program'. That
> way it won't starve everything else for I/O cycles. Also, you may want
> to experiment with using the 'deadline' elevator instead of the default
> 'cfq' (see http://www.redhat.com/magazine/008jun05/features/schedulers/
> and http://www.wlug.org.nz/LinuxIoScheduler). Neither of those would
> require you to change your hardware out. Also, setting 'noatime' for the
> mount options for partition holding the files will reduce the number of
> required I/Os quite a lot.
>
> But yes, in general, distributing your load across more disks should
> improve your I/O profile.
>
> --
> Benjamin Franz
> _______________________________________________
>
Can one mount the root filesystem with noatime?
--
Kind Regards
Rudi Ahlers
SoftDux
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