[zfs-discuss] raidz space overheads

Bill McGonigle bill at bfccomputing.com
Wed Dec 14 23:45:13 EST 2011

On 12/14/2011 01:28 PM, Gordan Bobic wrote:

> What this means is that to have minimum wasteage, you want the disk
> number that is power of 2 + redundancy, e.g. optimal number for Linear
> might be 2, 4, 8, 16, etc. disks.
> For RAIDZ1 you want Linear+1, i.e. 3, 5, 9, 17, etc.
> For RAIDZ2 you want Linear+2, i.e. 4, 6, 10, 18, etc.
> For RAIDZ3 you want Linear+3, i.e. 5, 7, 11, 19, etc.

And you want to hit these disk counts for performance too - if I had 12
2TB disks for a raidz2, I'd set up 10 disks plus two hot spares (it's
amazing how fast you can find yourself needing them).   Unless
performance really doesn't matter and space is the highest goal.


Bill McGonigle, Owner
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