From: mark@mark.mielke.cc
To: Rajesh Kumar Mallah <mallah.rajesh@gmail.com>
Cc: Luke Lonergan <llonergan@greenplum.com>
Cc: Michael Stone <mstone+postgres@mathom.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: setting up raid10 with more than 4 drives
Date: Wed, 30 May 2007 16:41:34 -0400
Message-ID: <20070530204134.GA20983@mark.mielke.cc> (raw)
In-Reply-To: <a97c77030705301258u1ef4e895h8fd32bfcadf22248@mail.gmail.com>
References: <C3E62232E3BCF24CBA20D72BFDCB6BF802AF2F1B@MI8NYCMAIL08.Mi8.com>
<C282EBA1.31B8C%llonergan@greenplum.com>
<20070530155733.GA18830@mark.mielke.cc>
<a97c77030705301258u1ef4e895h8fd32bfcadf22248@mail.gmail.com>
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.
Then comes the other factors. Do you want redundancy? Then you want 1.
Do you want capacity? Then you want 0.
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.
Cheers,
mark
--
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To: pgsql-performance@postgresql.org
Cc: mark@mark.mielke.cc, mallah.rajesh@gmail.com, llonergan@greenplum.com, mstone+postgres@mathom.us
Subject: Re: setting up raid10 with more than 4 drives
In-Reply-To: <20070530204134.GA20983@mark.mielke.cc>
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