From: Greg Smith <gsmith@gregsmith.com>
To: pgsql-performance@postgresql.org
Subject: Re: SCSI vs SATA
Date: Fri, 6 Apr 2007 16:44:19 -0400 (EDT)
Message-ID: <Pine.GSO.4.64.0704061558080.409@westnet.com> (raw)
In-Reply-To: <1175872847.9839.146.camel@state.g2switchworks.com>
References: <HCEPKPMCAJLDGJIBCLGHEENIHGAA.james@mansionfamily.plus.com>
<1175807611.9839.120.camel@state.g2switchworks.com>
<Pine.GSO.4.64.0704060019020.7614@westnet.com>
<1175872847.9839.146.camel@state.g2switchworks.com>
On Fri, 6 Apr 2007, Scott Marlowe wrote:
> Most server drives are rated for 55-60C environmental temperature
> operation, which means the drive would be even hotter.
I chuckled when I dug into the details for the drives in my cheap PC; the
consumer drives from Seagate:
http://www.seagate.com/docs/pdf/datasheet/disc/ds_barracuda_7200_10.pdf
are rated to a higher operating temperature than their enterprise drives:
http://www.seagate.com/docs/pdf/datasheet/disc/ds_barracuda_es.pdf
They actually have an interesting white paper on this subject. The factor
they talk about that isn't addressed in the studies we've been discussing
is the I/O workload of the drive:
http://www.seagate.com/content/pdf/whitepaper/TP555_BarracudaES_Jun06.pdf
What kind of sticks out when I compare all their data is that the chart in
the white paper puts the failure rate (AFR) of their consumer drives at
almost 0.6%, yet the specs on the consumer drive quote 0.34%.
Going back to the original question here, though, the rates are all
similar and small enough that I'd take many more drives over a small
number of slightly more reliable ones any day. As long as you have a
controller that can support multiple hot-spares you should be way ahead.
I get more concerned about battery backup cache issues than this nowadays
(been through too many extended power outages in the last few years).
> I do think that server grade drive tech has been migrating into the
> consumer realm over time. I can imagine that today's high performance
> game / home systems with their heat generating video cards and tendency
> towards RAID1 / RAID0 drive setups are pushing the drive manufacturers
> to improve reliability of consumer disk drives.
The introduction of fluid dynamic motor bearings into the hard drive
market over the last few years (ramping up around 2003) has very much
transformed the nature of that very temperature sensitive mechanism.
That's the cause of why a lot of rules of thumb from before that era don't
apply as strongly to modern drives. Certainly that fact that today's
consumer processors produce massively more heat than those of even a few
years ago has contributed to drive manufacturers moving their specs
upwards as well.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
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To: pgsql-performance@postgresql.org
Cc: gsmith@gregsmith.com
Subject: Re: SCSI vs SATA
In-Reply-To: <Pine.GSO.4.64.0704061558080.409@westnet.com>
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