Re: setting up raid10 with more than 4 drives

On 5/31/07, mark(at)mark(dot)mielke(dot)cc <mark(at)mark(dot)mielke(dot)cc> wrote:
> On Thu, May 31, 2007 at 01:28:58AM +0530, Rajesh Kumar Mallah wrote:
> > i am still not clear what is the best way of throwing in more
> > disks into the system.
> > does more stripes means more performance (mostly) ?
> > also is there any thumb rule about best stripe size ? (8k,16k,32k...)
>
> It isn't that simple. RAID1 should theoretically give you the best read
> performance. If all you care about is read, then "best performance" would
> be to add more mirrors to your array.
>
> For write performance, RAID0 is the best. I think this is what you mean
> by "more stripes".
>
> This is where RAID 1+0/0+1 come in. To reconcile the above. Your question
> seems to be: I have a RAID 1+0/0+1 system. Should I add disks onto the 0
> part of the array? Or the 1 part of the array?

> My conclusion to you would be: Both, unless you are certain that you load
> is scaled heavily towards read, in which case the 1, or if scaled heavily
> towards write, then 0.

thanks . this answers to my query. all the time i was thinking of 1+0
only failing to observe the 0+1 part in it.

>
> Then comes the other factors. Do you want redundancy? Then you want 1.
> Do you want capacity? Then you want 0.

Ok.

>
> There is no single answer for most people.
>
> For me, stripe size is the last decision to make, and may be heavily
> sensitive to load patterns. This suggests a trial and error / benchmarking
> requirement to determine the optimal stripe size for your use.

thanks.
mallah.

>
> Cheers,
> mark
>
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