Re: Software RAID-0 striping over Hardware RAID-5

On Mon, 20 Sep 2004 at 9:49am, AndyLiebman@aol.com wrote

Have you ever tested your systems while one of your RAID5 arrays is 
rebuilding or verifying? (I'm about to do that right now). I'm wondering if Linux 
Software RAID-0 might falter if one of the two arrays is significantly slower than 
the other (while rebuilding)?

I've had arrays under normal (sporadically heavy) usage during a rebuild, 
and there wasn't a problem.

My inclination is to not use a hot spare. Instead, I rely on 3ware's email 
notification feature to alert me that a drive needs to be replaced. I always 
keep a spare handy that can be popped into place immediately. Also, I want to 
have control over when rebuilding takes place. It would be a bad thing to rebuild 
during certain critical high I/O moments of the day -- whereas rebuilding at 
night would be much less stressful on the system. Do you see anything wrong 
with this approach? 

Yes -- it requires you to be on call 24x7 for maximum protection.  And 
even then the level of protection is less than with a hot spare, given 
that it will take you time to get from whereever you are to whereever the 
server is.  Also, disks can sometimes have a tendency to go in quick 
succession.  I would *strongly* recommend a hot spare.

Remember, you're cutting your reliability in half by striping the two 
arrays.  Why not maximally protect those individual arrays?

-- 
Joshua Baker-LePain
Department of Biomedical Engineering
Duke University