[Beowulf] Surviving a double disk failure

Guy Coates gmpc at sanger.ac.uk
Sun Apr 12 05:51:45 EDT 2009


Stuart Midgley wrote:
> Thanks to all the responses, it has been interesting reading.  We have
> started using raid6 on newer servers and will slowely get rid of our old
> raid5 servers.
> 
> I found the comments about scrubbing very interesting.  What do people
> do with their file systems?  We couldn't afford the reduced performance
> and time for scrubbing. 

You can set limits on how much IO a raid scrub or rebuild is going to
use by setting:

/proc/sys/dev/raid/speed_limit_max
/proc/sys/dev/raid/speed_limit_min

The default for speed_limit_min is pretty small, so you probably won't
notice much in the way of performance degradation. It might take a while
to complete though if your filesystems are busy.


Cheers,

Guy

-- 
Dr Guy Coates,  Informatics System Group
The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1HH, UK
Tel: +44 (0)1223 834244 ex 6925
Fax: +44 (0)1223 496802


-- 
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