Re: BBU still needed with SSD?

* 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(at)bfk(dot)de>
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