Re: Why do I need 4 disks for a raid6?

Andre Noll [off-list ref] writes:

On 08:34, Ruslan Sivak wrote:

quoted

I would guess the reason is that it doesn't make sense.  As mentioned, if
you are going to create a 3 disk raid 6, it's essentially a raid1 over 3
disks, at which point you are better off with the raid-1.  I don't think
there's a raid controller that would let you set something like this up, I
don't see why the softraid should.

Well, Goswin mentioned some pretty good reasons I think.

Andre
-- 
The only person who always got his work done by Friday was Robinson Crusoe

Raid6 is the only level that requires such "sanity".

Here is another scenario: Say you have a 2 disk raid1 and now want to
switch to 5 disk raid6. No problem, add 3 new disks, set up 1+2 disk
raid6, pvmove the data (don't you love LVM?), stop the raid1, grow the
raid6 to 5 disks.

It is clear that 1+2 disk raid6 only makes sense as a transitory step
but one that is usefull.

MfG
        Goswin