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User profile for user: MacMonkey
MacMonkey Author
User level: Level 1
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Replacing RAID Drives - go larger or smaller?

Hey guys,
One of my RAID Drives has failed and our supplier cannot get the same capacity drive to replace the broken one, is it okay to install a smaller drive while the others are bigger?

Message was edited by: Host <to clarify Subject>

G4 17" Powerbook, Mac OS X (10.5.6)

Posted on Feb 23, 2009 7:15 AM

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User profile for user: Camelot
Camelot
User level: Level 9
54,333 points

Feb 23, 2009 9:15 AM in response to MacMonkey

Smaller? Absolutely not.
Larger may be OK.

At lot of it depends on the RAID format you're using. If you're using a RAID format that spreads data across multiple disks (such as RAID 1, RAID 10 or RAID 5) then the size of the volume will be based on the smallest drive in the array.

So if you were using, say, seven 500GB drives in a RAID 5 array you'd end up with a 3TB volume (6 x 500GB + 1 disk for parity). Replace one of those 500GB drives with a 400GB drive and the RAID would require all the disks to be 400GB, resulting in a 2.4TB volume (6 x 400 + 1 disk for parity). Any extra space on any other drive is just lost.

Therefore you need to use a drive that is larger than the existing drives in your RAID set.
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Replacing RAID Drives - go larger or smaller?

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