From: | "Rajesh Kumar Mallah" <mallah(dot)rajesh(at)gmail(dot)com> |
---|---|
To: | "mark(at)mark(dot)mielke(dot)cc" <mark(at)mark(dot)mielke(dot)cc> |
Cc: | "Luke Lonergan" <llonergan(at)greenplum(dot)com>, "Michael Stone" <mstone+postgres(at)mathom(dot)us>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: setting up raid10 with more than 4 drives |
Date: | 2007-05-31 01:54:40 |
Message-ID: | a97c77030705301854y7c24355cu3b8a1d911cea1b92@mail.gmail.com |
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Lists: | pgsql-performance |
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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