Whoa... Thank you so much for pointing out the issue with overlays. There seems to be no real consensus on what should be used. Could you talk about what should be used?
Devicemapper works (make sure you don't use loop devices) okay. Unfortunately it's slow to warm up, but it's probably the most tested storage driver (it's the default on a bunch of systems).
btrfs works pretty well and is quite a bit faster. It's the default for SLE and openSUSE (as well as other distros which use btrfs by default). I'd recommend it (but I can't remember if it requires you to use btrfs on your / partition, which might be an issue for you).
ZFS, while being an awesome filesystem, I doubt has had much testing under Docker, so I'd be wary about using it.
And I've already told you what I thought about overlay. I'd like to point out that it's a good filesystem for what it was designed for (persistent or transient livecds) but the hacks in Docker in order to use it for their layering keeps me up at night.
Yeah - all of which mean that I have to move away from Linode.
They can't backup anything other than a vanilla ext4 volume. I setup a direct lvm docker vm on Linode (was surprisingly easy) - but Linode is refusing to back it up.
If Linode supports ZFS, you could use ZFS send-recieve to make backups to your local machine. But like I said, the ZFS storage driver probably hasn't been well tested.
nope. no backup for anything other than EXT4. Its really weird and limiting.
I mean LVM volumes have to be pretty standard right ? (I would argue more standard than ZFS).
Just FYI - we use Debian on Linode.