[ale] Need an off the shelf linux recommendation

[Greg Freemyer]

On Wed, 2004-02-04 at 16:45, Dow Hurst wrote:
> I thought 0+1 was mirroring two drives?  Is it two mirrors 
> of two drives?
> Dow
> 

0 = striping  (ie. no fault tolerance, done for performance reasons.)
1 = mirroring (fault tolerant) 

I have trouble remembering which is 0+1 and 1+0, but each takes 4 drives
minimum.  The max. drives in either is hardware/software specific.

I think 0+1 is 2 stripsets mirrored together.

1+0 is 2 mirrorsets striped together.

The best way is mirrorsets striped together.  It can survive more 2
drive failures than if you set it up the other way around.

ie.
A 4-disk RAID 1+0 setup will survive 2/3 of all 2 disk failures.
A 4-disk RAID 0+1 setup will only survive 1/3 of all 2 disk failures.

A 10-disk RAID 1+0 setup will survive 8/9 of all 2 disk failures.
A 10-disk RAID 0+1 setup will only survive 4/9 of all 2 disk failures.


Greg
-- 
Greg Freemyer