[SATLUG] 1st question - RAID5 quit - Short tests completed

Samuel Leon satlug at net153.net
Mon Aug 17 08:55:51 CDT 2009


David Labens wrote:
> SDA = # 1  Short offline       Completed without error       00%      5841         -
> SDB = # 1  Short offline       Completed without error       00%      5828         -
> SDC = # 1  Short offline       Completed: read failure       90%      5829         166       89727
> SDE = # 1  Short offline       Completed without error       00%      5824         -
> 
> So, this means SDC failed?  Physical problems?  
> 
> But, I should still be able to get the other 3 to mount & have the RAID5 repair itself, right?

True but the problem is that one of those drives could have been knocked 
out of the array many months ago.  The only reason you noticed was that 
another drive failed recently and caused filesystem issues.  So you 
really can't force the array to rebuild with 3 out of 4 disks if one of 
those disks contains very old data.  See how raid5 works here, 
specifically the xor summing: 
http://www.scottklarr.com/topic/23/how-raid-5-really-works/


Since we now know that sdc is in trouble, you might be able to get a 
replacement drive and try to copy the data over block by block.  And 
then use that drive in the array.  More than likely forcing the array to 
rebuild with this bad drive in it will cause problems.  So we don't want 
to do that yet.  I guess we will wait and see what Don has to say about 
the matter :)

Sam


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