From: Dimitri Fontaine <dfontaine@hi-media.com>
To: pgsql-performance@postgresql.org
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Vivek Khera <khera@kcilink.com>
Subject: Re: dell versus hp
Date: Thu, 8 Nov 2007 21:14:36 +0100
Message-ID: <200711082114.36788.dfontaine@hi-media.com> (raw)
In-Reply-To: <dcc563d10711081022i9a8a64fg2fe00e6159027426@mail.gmail.com>
References: <82607932-FC46-4B73-BF78-2290EE55F7F5@pvv.ntnu.no>
<44B74F2E-29A6-4746-B8A8-E9355CC2F527@kcilink.com>
<dcc563d10711081022i9a8a64fg2fe00e6159027426@mail.gmail.com>
Le Thursday 08 November 2007 19:22:48 Scott Marlowe, vous avez écrit :
> On Nov 8, 2007 10:43 AM, Vivek Khera <khera@kcilink.com> wrote:
> > On Nov 6, 2007, at 1:10 PM, Greg Smith wrote:
> > > elsewhere. But once you have enough disks in an array to spread all
> > > the load over that itself may improve write throughput enough to
> > > still be a net improvement.
> >
> > This has been my expeience with 14+ disks in an array (both RAID10 and
> > RAID5). The difference is barely noticeable.
>
> Mine too.
May we conclude from this that mixing WAL and data onto the same array is a
good idea starting at 14 spindles?
The Dell 2900 5U machine has 10 spindles max, that would make 2 for the OS
(raid1) and 8 for mixing WAL and data... not enough to benefit from the move,
or still to test?
> I would suggest though, that by the time you get to 14
> disks, you switch from RAID-5 to RAID-6 so you have double redundancy.
> Performance of a degraded array is better in RAID6 than RAID5, and
> you can run your rebuilds much slower since you're still redundant.
Is raid6 better than raid10 in term of overall performances, or a better cut
when you need capacity more than throughput?
Thanks for sharing the knowlegde, regards,
--
dim
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To: pgsql-performance@postgresql.org
Cc: dfontaine@hi-media.com, scott.marlowe@gmail.com, khera@kcilink.com
Subject: Re: dell versus hp
In-Reply-To: <200711082114.36788.dfontaine@hi-media.com>
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