[SATLUG] Understanding RAID and global hot spares

David Salisbury david.salisbury at momentumweb.com
Thu Dec 17 16:56:30 CST 2009

I've got a server-type box with an Intel RAID controller running SUSE 
Enterprise.  One array with some 160g drives (3 in RAID 1 [2 plus a 
global hot spare]), and the 2nd array with some terabyte drives (3 in 
RAID 1 [2 plus a global hot spare]).  Since I assigned each of those hot 
spares to the respective RAID array (the 160g hot spare to the 160 
array, the 1TB hot spare to the terabyte array), I was under the 
impression each hot spare would be used in each array, respectively.

But, in testing this setup, I pulled a drive from the 160g array and it 
started using the terabyte hot spare to rebuild the array!!  Not what I 
wanted to have happen.  (I had already tested this once before, and it 
used the correct 160g hot spare.  But this 2nd time it used the 1TB 
drive.)  Am I not understanding the global hot spare?  Do I need to 
configure the global hot spare to be "local" or something so that it 
doesn't hop arrays like that?  If I DO have to do that, will 
reconfiguring the RAID array mess with or destroy the data on the drives 
I already have running?


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