On Tue, Apr 12, 2011 at 8:56 AM, <rainer@xxxxxxxxxxxxxxx> wrote:
That's not the issue.
The issue is rebuild-time.
The longer it takes, the more likely is another failure in the array.
With RAID6, this does not instantly kill your RAID, as with RAID5 - but I
assume it will further decrease overall-performance and the rebuild-time
will go up significantly - adding the the risk.
Thus, it's generally advisable to do just use RAID10 (in this case, a
thin-striped array of RAID1-arrays).
Statistically speaking that risk isn't there. RAID6 arrays have a slightly higher mean time between dataloss than RAID10's. But the difference here is very small. So if you need the capacity and don't mind the performance difference between these two RAID levels then RAID6 is perfectly fine in my opinion.
Here's a great blog post on calculating Mean Time Between Dataloss and they have a spreadsheet that you can download to play with. http://info.zetta.net/blog/bid/45661/Calculating-Mean-Time-To-Data-Loss-and-probability-of-silent-data-corruption
In my configuration which is 12 drives the chances of a dataloss event over a 10 year period with RAID10 is 2.51% and with RAID6 is 1.31%. I would expect those numbers to go up a bit with 16 drive configuration.
--
David
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