[CentOS] disk I/O problems and Solutions

[Brian Mathis]

On Fri, Oct 9, 2009 at 1:55 PM, Alan McKay <alan.mckay at gmail.com> wrote:
>> Since you stated that your system is only having trouble at writes,
>> doing batch inserts, I would look at how you are doing these batch
>> inserts and see if you can optimize this by using techniques to delay
>> key writes or adjust locking mechanisms on the insert. Some databases
>> have special insert from file or bulk insert operations that are much
>> faster than running many single row inserts - be sure you are taking
>> advantage of these methods.
>
> Yeah, our DB geeks have already said a few weeks ago that they think
> we are doing these bulk updates in a pretty inefficient manner, so
> that's something else we plan to optimize.
>

In addition to the suggestions above (you should definitely be doing
RAID10), take a look at the wiki page on optimizing the disks
(http://wiki.centos.org/HowTos/Disk_Optimization).  Pay special
attention to the sections on "noatime" and "RAID Math", which deals
with making sure the filesystem blocks are aligned with the RAID
blocks, which can potentially reduce your IOPS per write, giving a
reported 15-25% performance improvement.  I think the wiki page isn't
totally up to date, but it's a good starting point on the concept.