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.kirkwood@xxxxxxxxxxxxxxx>
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
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