Re: Advice configuring ServeRAID 8k for performance

On 06/08/10 11:58, Alan Hodgson wrote:
> On Thursday, August 05, 2010, Mark Kirkwood<mark.kirkwood@catalyst.net.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.

Cheers

Mark