[Beowulf] Re: Large raid rebuild times

Joe Landman landman at scalableinformatics.com
Fri Nov 20 09:32:08 EST 2009


Robert Sandilands wrote:
> I am currently rebuilding a 28 x 1 TB RAID 5 volume that is based on the 

Hmmm....

> SurfRAID TRITON 16S3 with a JBOD unit. It is 16.6% complete after 2 1/2 
> hours.
> 
> I am rebuilding before copying the data and returning all the Seagate 1 
> TB drives. Replacing it with Hitachi 2 TB drives and RAID 6.
> 
> The combination of a large number of drives in RAID 5 and/or Seagate 1 
> TB drives is not to be recommended.

Actually, you shouldn't be using RAID5 any more.  The bit error rates 
suggest that you will in all likelihood, hit an uncorrectable error 
within a very small number of rebuilds, and lose data.

This is fairly well known at this point, so I have to admit surprise to 
hear of anyone using 20+ drives of TB size in a RAID5.

On Seagate, YMMV, they have been rock solid for us and our customers 
(thousands shipped, scales of PBs of storage).  Failure rates somewhat 
above their statistical estimates, very much in line with what Google 
indicates they have observed with their drives.

We haven't used Hitachi very much in our units, so I can't comment much 
on their quality/failure rate.

Joe



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Joseph Landman, Ph.D
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