Re: RAID-6 support in kernel?

Hi!

quoted

quoted

It'll waste 9 drives, giving me a total capacity of 7n instead of 14n. 
And, by definition, RAID-6 _can_ withstand _any_ two-drive failure.

This is certainly not true. 

Combining N RAID-5 into a stripe wastes on N disks. 

If you combine two it wastes 2 disks, etc.

That is, for each RAID-5 you waste a single disk worth of storage for
partiy. I don't know what equation you're using where you get 9 drives
from.

He was thinking "mirror", not "stripe". Mirror of 2 RAID-5 arrays (would
be probably called RAID-15 (when there is a RAID-10 for mirrored stripe
arrays)), can withstand any two disks failing anytime. Even more for

RAID-1 over two RAID-5s should withstand any three failures, AFAICS.

You could do RAID-5 over RAID-5. That should survive any 2 failures and
still be reasonably efficient.
								Pavel
-- 
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.