[Discuss] On Btrfs raid and odd-count disks

[Richard Pieri]

On 4/10/2013 11:39 AM, Shirley Márquez Dúlcey wrote:
> also on drive B and the other half is on drive C. (It's similar for
> drives B and C.) In a five disk set, the other copy of data from drive
> A would be distributed among drives B, C, D, and E.

Correct, although with 5 disks you can engage raid10 mode: striping in
addition to replication. This may be where Ned is getting his
comparisons to RAID 1e. But it isn't RAID 1e. No effort is made to
achieve ~(n>1) fault tolerance.

You don't have to use raid10 mode with five disks. You can use raid1
mode. You might use raid1 mode if you layer Btrfs on top of SAN LUNs
that have striping at the physical device level and you've chosen to do
mirroring on the host rather than on the SAN. I can't think of a
configuration where this makes any sense but that's a different issue.

-- 
Rich P.