[Beowulf] Surviving a double disk failure

[Joe Landman]

Orion Poplawski wrote:
> Joe Landman wrote:
>> Stuart Midgley wrote:
>>
>> Good work Stuart!
>>
>>> What are the lessons learnt? Well with software raid Linux is both your 
>>
>> 1) Use RAID6.  It is your friend.  RAID5 is unashamedly your enemy.
> 
> So, what's a reasonably limit on the number of disks in a RAID6 array 
> using 1.5TB disks?

We have 1 customer using 24 drives (22 for data with 2 hot spares) as an 
md raid6 on DeltaV.  Normally we'd suggest something smaller 
(collections of RAID6 and then striping across them to form RAID60's).

With late model kernels, mdadm, and using 1.2 metadata on the md's, you 
should be able to build fairly sizeable stripe width devices.  I've 
heard limits of 255, but never tested this far out.

-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
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