Re: Advice on raid/lvm

On Wed, Apr 08, 2009 at 11:57:59AM -0700, Mike Castle (dalgoda+debian@xxxxxxxxx) wrote:

On Wed, Apr 8, 2009 at 7:34 AM, Kelly Harding <kelly.harding@xxxxxxxxx> wrote:

Aiming to get a couple of 1Tb drives to migrate the 3x500Gb RAID5
array to a RAID1 and use two of the 500Gb drives for thhe new boot
drive with LVM (With /boot / /home and so on on it).

with today's larger disks, the time it takes to do a
rebuild is sufficiently long enough that the risk of a second drive
failure during the rebuild is high enough to be troublesome.

That is true - but moving from RAID5 to RAID1 will improve the odds.
If the quality of the disks is same, probability of an unrecoverable
read error in one 1TB disk should be same in one of two 500GB disks,
and the probability of whole disk failure is bigger with 2 disks.
Moreover, RAID5 rebuild is much slower than RAID1 - I don't have
hard data at hand, but I think rebuilding 3x500GB RAID5 would
take longer than 2x1TB RAID1.
So 2x1TB as RAID1 is safer than 3x500GB as RAID5.

--
Tapani Tarvainen


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