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Message-ID: <dcc563d10711081022i9a8a64fg2fe00e6159027426@mail.gmail.com>
Date: Thu, 8 Nov 2007 12:22:48 -0600
From: "Scott Marlowe" <scott.marlowe@gmail.com>
To: "Vivek Khera" <khera@kcilink.com>
Subject: Re: dell versus hp
Cc: "PostgreSQL Performance" <pgsql-performance@postgresql.org>
In-Reply-To: <44B74F2E-29A6-4746-B8A8-E9355CC2F527@kcilink.com>
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References: <82607932-FC46-4B73-BF78-2290EE55F7F5@pvv.ntnu.no>
	<200711061253.46756.dfontaine@hi-media.com>
	<Pine.GSO.4.64.0711061302140.523@westnet.com>
	<44B74F2E-29A6-4746-B8A8-E9355CC2F527@kcilink.com>

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.  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.

> If the PERC5/i is an Adaptec card, run away.

I've heard the newest adaptecs, even the perc implementations aren't bad.

Of course, that doesn't mean I'm gonna use one, but who knows?  They
might have made a decent card after all.