[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

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