From: Grega Bremec <gregab@p0f.net>
To: Hannes Dorbath <light@theendofthetunnel.de>
Cc: pgsql-general@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Arguments Pro/Contra Software Raid
Date: Tue, 09 May 2006 13:37:03 +0200
Message-ID: <44607EDF.60109@p0f.net> (raw)
In-Reply-To: <e3pmkc$12mk$1@news.hub.org>
References: <e3pmkc$12mk$1@news.hub.org>
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Hannes Dorbath wrote:
> Hi,
>
> I've just had some discussion with colleagues regarding the usage of
> hardware or software raid 1/10 for our linux based database servers.
>
> I myself can't see much reason to spend $500 on high end controller
> cards for a simple Raid 1.
>
> Any arguments pro or contra would be desirable.
>
One pro and one con off the top of my head.
Hotplug. Depending on your platform, SATA may or may not be hotpluggable
(I know AHCI mode is the only one promising some kind of a hotplug,
which means ICH6+ and Silicon Image controllers last I heard). SCSI
isn't hotpluggable without the use of special hotplug backplanes and
disks. You lose that in software RAID, which effectively means you need
to shut the box down and do maintenance. Hassle.
CPU. It's cheap. Much cheaper than your average hardware RAID card. For
the 5-10% overhead usually imposed by software RAID, you can throw in a
faster CPU and never even notice it. Most cases aren't CPU-bound
anyways, or at least, most cases are I/O bound for the better part. This
does raise the question of I/O bandwidth your standard SATA or SCSI
controller comes with, though. If you're careful about that and handle
hotplug sufficiently, you're probably never going to notice you're not
running on metal.
Kind regards,
- --
Grega Bremec
gregab at p0f dot net
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To: pgsql-performance@postgresql.org
Cc: gregab@p0f.net, light@theendofthetunnel.de, pgsql-general@postgresql.org
Subject: Re: [PERFORM] Arguments Pro/Contra Software Raid
In-Reply-To: <44607EDF.60109@p0f.net>
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