On 2013/04/11 10:36 AM, Joseph Spenner wrote:
> ________________________________
> From: John R Pierce <pierce@xxxxxxxxxxxx>
> To: centos@xxxxxxxxxx
> Sent: Thursday, April 11, 2013 1:24 PM
> Subject: Re: RAID 6 - opinions
>
>
> On 4/11/2013 12:30 PM, m.roth@xxxxxxxxx wrote:
>>> Ok, listening to all of this, I've also been in touch with a tech from the
>>> vendor*, who had a couple of suggestions: first, two RAID sets with two
>>> global hot spares.
>
> I would test how long a drive rebuild takes on a 20 disk RAID6. I
> suspect, very long, like over 24 hours, assuming a fast controller and
> sufficient channel bandwidth.
>
> ----
>
> But isn't that one of the benefits of RAID6? (not much degraded/latency effect during a rebuild, less impact on performance during rebuild, so longer times are acceptable?)
>
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Besides performance, the longer your rebuild takes, the more vulnerable
you are to additional disk failure taking out your array. We've lost
arrays that way in the past, pre-RAID6, lost two disks within a 6-hour
period, and there went the array since the rebuild wasn't complete.
RAID6 means you can handle 2 disk failures, but the third one will drop
your array, if I'm remembering correctly. And the larger the number of
disks, the higher the chance that you'll have disk failures...
Thanks!
Miranda
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