Experiences with LVM vs btrfs

[Andrew J. Caines]

Petter,

> The system is on two 250G drives in RAID1 (now mdadm, xfs), and I
> specifically want snapshots, subvolumes would also be nice. What I
>  would like to know, is: should I put LVM on top of the RAID, or
> should I dispense of mdadm altogether and let btrfs take care of
> everything?

Which did you choose and what have you experienced so far?

My 12.04 desktop used md for the three 1 TB disk RAID 5 and has been
faultless in the 4.5 years it has run [I say with no sense of hubris].
The btrfs v0.19 on it has also behaved well, though I've not used any
interesting features.

My media PC runs 14.04 and uses a btrfs v3.12 RAID 1 across two 1 TB
disks with subvolumes and apart from causing a little confusion to
gnome-disks about what's on what disk*, it has also run flawlessly for
maybe a year since being built. I've not played with snapshots.

The various btrfs docs are still full of overly conservative warnings,
but in my experience the basic functionality is solid and I have no lost
any data to the filesystem - something I cannot say of the ext family.

> (Oh, I am aware that I must stop using xfs, as it can't shrink
> volumes.)

FWIW, RHEL dropped ext4 in favour of XFS in the current version (7).
Filesystems rarely shrink.

> Can someone who has experience with LVM and/or btrfs give me some
> advice on what is the best to work with, easiest to learn, requires
>  little maintenance, etc?

Start with btrfs since it's both volume manager and filesystem, inspired
by the widely-deployed-in-the-real-world ZFS and reasonably mature. You
are already doing it right by having working backups and reasonable
expectations of performance.

> What would the experts out there recommend to someone who is new
> to both?

No idea, but interested to find out. What did they say?


*[The two disks in a USB enclosure show as one WDC disk with a 1 TB
  unknown filesystem and two ORICO disks with a 1 TB btrfs, only one
  of which is mounted.]

-- 
-Andrew J. Caines-   Unix Systems Engineer   A.J.Caines at halplant.com
  "Machines take me by surprise with great frequency" - Alan Turing


-- 
-Andrew J. Caines-   Unix Systems Engineer   A.J.Caines at halplant.com
  "Machines take me by surprise with great frequency" - Alan Turing