Re:Btrfs has been deprecated in RHEL
by rodgerd on Thursday August 03, 2017 @06:27PM
(#14924528)
The design of btrfs allows for mismatched disks to be used in an array, and the btrfs RAID will keep the right level of redundancy while using the maximal amount of space, e.g. with a 4 TB, 2 TB, and 1 TB drive:
mdadm will give you 1 TB in RAID 1, or 1.5 TB in RAID 10 (constrained by the smallest drive).
btrfs will give you 3 TB in RAID 1 (constrained by the sum of the smallest drives).
btrfs also allows per-subvolume raid policies. So you could, for example, give users an "archive" subvolume in their home directory. You could then mark this as RAID 1 or RAID 5 (because you don't care so much about performance) while the main /home filesystem is RAID 10.
Unfortunately the RAID code is all horribly broken.
mdadm will give you 1 TB in RAID 1, or 1.5 TB in RAID 10 (constrained by the smallest drive).
btrfs will give you 3 TB in RAID 1 (constrained by the sum of the smallest drives).
btrfs also allows per-subvolume raid policies. So you could, for example, give users an "archive" subvolume in their home directory. You could then mark this as RAID 1 or RAID 5 (because you don't care so much about performance) while the main /home filesystem is RAID 10.
Unfortunately the RAID code is all horribly broken.