From: Florian Weimer <fweimer@bfk.de>
To: Yeb Havinga <yebhavinga@gmail.com>
Cc: Andy <angelflow@yahoo.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: BBU still needed with SSD?
Date: Tue, 19 Jul 2011 10:47:07 +0000
Message-ID: <82y5zubl90.fsf@mid.bfk.de> (raw)
In-Reply-To: <4E255DF9.20005@gmail.com>
References: <1310953399.25726.YahooMailClassic@web111304.mail.gq1.yahoo.com>
<4E23E72B.2070508@gmail.com>
<82vcuyd7p5.fsf@mid.bfk.de>
<4E255DF9.20005@gmail.com>
* Yeb Havinga:
> On 2011-07-19 09:56, Florian Weimer wrote:
>> * Yeb Havinga:
>>
>>> The biggest drawback of 2 SSD's with supercap in hardware raid 1, is
>>> that if they are both new and of the same model/firmware, they'd
>>> probably reach the end of their write cycles at the same time, thereby
>>> failing simultaneously.
>> I thought so too, but I've got two Intel 320s (I suppose, the report
>> device model is "SSDSA2CT040G3") in a RAID 1 configuration, and after
>> about a month of testing, one is down to 89 on the media wearout
>> indicator, and the other is still at 96. Both devices are
>> deteriorating, but one at a significantly faster rate.
> That's great news if this turns out to be generally true. Is it on
> mdadm software raid?
Yes, it is.
It's a mixed blessing because judging by the values, one of the drives
wears down pretty quickly.
> Maybe it is caused by the initial build of the array? But then a 7%
> difference seems like an awful lot.
Both drives a supposedly fresh from the factory, and they started with
the wearout indicator at 100. The initial build should write just
zeros, and I would expect the drive firmware to recognize that.
I've got a second system against which I could run the same test. I
wonder if it is reproducible.
> It would be interesting to see if the drives also show total xyz
> written, and if that differs a lot too.
Do you know how to check that with smartctl?
--
Florian Weimer <fweimer@bfk.de>
BFK edv-consulting GmbH http://www.bfk.de/
Kriegsstraße 100 tel: +49-721-96201-1
D-76133 Karlsruhe fax: +49-721-96201-99
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To: pgsql-performance@postgresql.org
Cc: fweimer@bfk.de, yebhavinga@gmail.com, angelflow@yahoo.com
Subject: Re: BBU still needed with SSD?
In-Reply-To: <82y5zubl90.fsf@mid.bfk.de>
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