[ale] Confusing RAID Performance

[David Tomaschik]

On 02/02/2011 04:23 PM, Jeff Hubbs wrote:
> On 2/2/11 2:15 PM, scott wrote:
>> Remember that RAID6 is slower than RAID5.  RAID5 calculates the parity
>> once.  RAID6 does it twice.  This is to make sure that you have parity
>> protection incase you drop a drive. I would only recommend RAID6 on
>> large drives (1TB or larger).
> I sure wouldn't.  For >=~1TB drives, the probability of having an 
> unrecoverable read error among all the drives at recover time starts 
> becoming significant.  Sure, you can use it - as long as a restore from 
> tape, etc. is an acceptable fallback if you can't rebuild after a drive 
> replacement.

Actually, just 3 hours ago, I had a storage consultant telling me about
a whitepaper that indicated a 20%/year chance of failure on a 5-disk
RAID 5 of consumer grade SATA hard drives.  I can't find the paper he
refers to, and the numbers seem high to me, but hey, I'm not going to
chance it.

David