[Beowulf] Big storage

Andrew Piskorski atp at piskorski.com
Mon Aug 27 15:30:51 EDT 2007


On Mon, Aug 27, 2007 at 05:25:51AM -0500, Bruce Allen wrote:

> I did read Garth's comments. I believe that there are two types of 
> possible problems:
> 
> (1) A sector or handful of sectors on a disk become unreadable
> (2) An entire disk fails (all sectors become unreadable)
> 
> Problems of type (1) can be handled well by high quality raid 
> implementations.

I believe Garth's whole point is that your assumption above is often
NOT true.  He also seemed to imply that this is a function of the
ineraction between the block-level RAID implementation and the file
system, as his Panasas file system reputedly fixes this scary, "one
small unrecoverable read during array rebuild kills your entire disk
volume" failure mode.

However, I do not really understand exactly which systems are subject
to this risk of catastrophic failure and which are not, nor why.  If
anyone has pointers to a more complete explanation, please do chime
in...

-- 
Andrew Piskorski <atp at piskorski.com>
http://www.piskorski.com/
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