On Wed, 23 Jan 2013 11:35:09 -0500, James Holsenback wrote:

> On 01/23/2013 10:41 AM, Le_Forgeron wrote:
>> Le 23/01/2013 16:09, Cousin Ricky a écrit :
>>> for Linux is most emphatically that RAID must not be used as a primary
>>> backup system.
>>
>> If you expect RAID to cover failure, you would be in for deception.
> 
> /generally/ speaking that would be false, but yep I agree with you on
> this, as I've seen failures involving two different mechanisms and
> recovery was problematic ... worst case scenario who be a failure that
> also involved loss of the parity compressed data. In a /perfect/ world
> RAID5 is a valid option.

Oh yes, I would agree as well.  The Compaq SMART controller I just 
mentioned in response to Ricky had multiple two-drive failures (caused by 
inadequate cooling at the end of the hardware's useful life).

Less likely is if you have a hot spare (which the newer SMART controllers 
supported 10 years ago) or mirrored RAID-5 (sometimes called RAID10, 
sometimes called RAID15 - there was no industry standard at the time for 
what it was called).

It's all about mitigating risk, and to do that, you have to consider MTBF 
and the environment the hardware is in (and how that is likely to affect 
MTBF).

Jim

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