I need to create a raid10 array with btrfs. The raid will be handled by btrfs directly (not mdadm), since, I believe, it gives more information to the btrfs layer to detect and handle failures (am I right?).
So, it's easy: there is plenty of docs everywhere. I just have to use:
mkfs.btrfs -m raid10 -d raid10 /dev/sdb /dev/sdc /dev/sdd /dev/sde
Hold on: I explicitly bought two sets of drives from different manufacturers because this. So I need to know how mkfs.btrfs
will group drives in clusters.
So, if I use the above command example, will I get a
- (RAID0 over (/dev/sdb + /dev/sdc RAID1) and (/dev/sdd + /dev/sde RAID1)), or a
- (RAID0 over (/dev/sdb + /dev/sdd RAID1) and (/dev/sdc + /dev/sde RAID1)),
- or, as I'm starting to suspect, none of the above, the raid10 profile just guaranteeing each block to be duplicated on two distinct drives, but the choice of the drives being somewhat random (since apparently raid10 btrfs allows an odd number of drives, it certainly doesn't behave like regular raid 10).
This isn't quite clear in the docs, including in the appropriate man page.