From: | Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Advice configuring ServeRAID 8k for performance |
Date: | 2010-08-06 00:35:44 |
Message-ID: | 4C5B58E0.9060902@catalyst.net.nz |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
On 06/08/10 12:31, Mark Kirkwood wrote:
> On 06/08/10 11:58, Alan Hodgson wrote:
>> On Thursday, August 05, 2010, Mark
>> Kirkwood<mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
>> wrote:
>>> Normally I'd agree with the others and recommend RAID10 - but you say
>>> you have an OLAP workload - if it is *heavily* read biased you may get
>>> better performance with RAID5 (more effective disks to read from).
>>> Having said that, your sequential read performance right now is pretty
>>> low (151 MB/s - should be double this), which may point to an issue
>>> with this controller. Unfortunately this *may* be important for an OLAP
>>> workload (seq scans of big tables).
>> Probably a low (default) readahead limitation. ext3 doesn't help but
>> it can
>> usually get up over 400MB/sec. Doubt it's the controller.
>>
>
> Yeah - good suggestion, so cranking up readahead (man blockdev) and
> retesting is recommended.
>
>
... sorry, it just occurred to wonder about the stripe or chunk size
used in the array, as making this too small can also severely hamper
sequential performance.
Cheers
Mark
From | Date | Subject | |
---|---|---|---|
Next Message | Matthew Wakeling | 2010-08-06 09:17:06 | Re: Advice configuring ServeRAID 8k for performance |
Previous Message | Mark Kirkwood | 2010-08-06 00:31:50 | Re: Advice configuring ServeRAID 8k for performance |