[ale] Confusing RAID Performance

[David Tomaschik]

On 02/02/2011 06:43 PM, Greg Freemyer wrote:
> On Wed, Feb 2, 2011 at 6:11 PM, David Tomaschik
> <david at systemoverlord.com> wrote:
>> On 02/02/2011 04:23 PM, Jeff Hubbs wrote:
>>> 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
> 
> Seems low to me for 1 TB drives.  And I've run the numbers with 2 TB
> drives.  (I don't recall exactly what the results were off-hand.  But
> they were scary.)
> 
> Simply don't use raid 5 with large drives if you don't want to lose
> your array from time to time.
> 
> Greg
> 

That seems low?  I'm trying to calculate the numbers now, but figuring
out bitwise errors, MTBF, sectors, etc, has got me getting weird
results.  I'd rather just find the whitepaper from the storage experts.

David