[wplug] Hardware RAID tuning

Matthew Zwier mczwier at gmail.com
Wed Jun 15 15:28:08 EDT 2011


Yeah, I do.  Don't know if it matters, but the kernel's pretty old
(it's a Rocks 5.3 cluster) -- 2.6.18.

On Wed, Jun 15, 2011 at 3:24 PM, Max Putas <maxblaze at gmail.com> wrote:
> Do you have the latest firmware on your controller? MegaRAID is known
> to be a little wonky, and updates have fixed a few issues that I've
> seen in the past.
>
> On Wed, Jun 15, 2011 at 2:55 PM, Matthew Zwier <mczwier at gmail.com> wrote:
>> Hi all,
>>
>> Thanks, Nate, Nicholas, ans Martin for your help.  I appear to be
>> chasing Heisenbugs.  Today, all is much better.  I'm getting 250 MB/s
>> sustained write speeds on my RAID 5s and 330 MB/s on my RAID 50.  I'm
>> getting 250 MB/s sustained reads on my 7-disk RAID 5s and 320-400 MB/s
>> on my 15 disk RAID 50 and RAID 5 respectively, as measured with dd and
>> iotop.  Yesterday, the writes were topping out at 120 MB/s and the
>> reads at 40 MB/s by any test I chose to run.  I ran some filesystem
>> maintenence yesterday night, and the cluster is much more lightly
>> loaded, but that's all that's changed.
>>
>> Today, xfsdump is fluctuating between 360 MB/s, 20 MB/s, and 875 kB/s,
>> with the fluctuations correlating well with read accesses.  The
>> filesystem I'm dumping is mounted but isn't in use, so it must be
>> reads from other arrays on the same controller.  Could this be a
>> poorly-configured disk scheduler?
>>
>> Seeing as how sequential performance isn't really the 40 MB/s that I
>> feared, making this a problem with my backup idea instead of the RAID
>> array itself, I think I'll be trying something other than xfsdump.
>> rsync isn't the most palatable option (statting 37 million files takes
>> a long time), but just about anything is better than a 5-day-long
>> backup cycle.
>>
>> Thanks again,
>> MZ
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>>
>
>
>
> --
> Thanks,
>
> Max Putas
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>


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