[CentOS] Possible to use multiple disk to bypass I/O wait?

Emmanuel Noobadmin centos.admin at gmail.com
Thu Jun 9 16:48:23 UTC 2011


On 6/9/11, Benjamin Franz <jfranz at freerun.com> wrote:

> 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.

Thanks for pointing out noatime, I came across in my reading
previously but it never sunk in. This experience is definitely going
to make sure of that :)

Tthe crawl process is started by another program. crond starts the
program, the program starts the email crawl or take other more crucial
action depending on situation so I'm unsure if I should run it with
ionice since it could potentially cause the more crucial action to
lag/slow down.

But I'll give it a try anyway over the weekend when any negative
effect has lesser consequences and see if it affects other things.

> But yes, in general, distributing your load across more disks should
> improve your I/O profile.

I'm going with noatime and ionice first to see the impact before I
start playing around with the i/o scheduler. If all else fails, then
I'll see about requesting for the extra hard disk.



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