Re: RAID Stripe size

I have benched different sripe sizes with different file systems, and the
perfmance differences can be quite dramatic.

Theoreticaly a smaller stripe is better for OLTP as you can write more small
transactions independantly to more different disks more often than not, but
a large stripe size is good for Data warehousing as you are often doing very
large sequential reads, and a larger stripe size is going to exploit the
on-drive cache as you request larger single chunks from the disk at a time.

It also seems that different controllers are partial to different defaults
that can affect their performance, so I would suggest that testing this on
two different controller cards man be less than optimal.

I would also recommend looking at file system. For us JFS worked
signifcantly faster than resier for large read loads and large write loads,
so we chose JFS over ext3 and reiser.

I found that lower stripe sizes impacted performance badly as did overly
large stripe sizes.

Alex Turner
NetEconomist

On 16 Sep 2005 04:51:43 -0700, bmmbn <miki(at)canaan(dot)co(dot)il> wrote:
>
> Hi Everyone
>
> The machine is IBM x345 with ServeRAID 6i 128mb cache and 6 SCSI 15k
> disks.
>
> 2 disks are in RAID1 and hold the OS, SWAP & pg_xlog
> 4 disks are in RAID10 and hold the Cluster itself.
>
> the DB will have two major tables 1 with 10 million rows and one with
> 100 million rows.
> All the activities against this tables will be SELECT.
>
> Currently the strip size is 8k. I read in many place this is a poor
> setting.
>
> Am i right ?
>
>
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