[lxc-users] LXD - upgrade from 2.08 to 2.12 enables BTRFS quota

[Stéphane Graber]

On Sun, Jun 04, 2017 at 08:36:28AM -0400, Ron Kelley wrote:
> Greetings all.
> 
> I recently upgraded a number of LXD 2.08 servers to 2.12 and noticed the btrfs “quota” option was enabled where it was disabled before.  Enabling quotas on a filesystem with lots of snapshots can cause huge performance issues (as indicated by our 20min outage this morning when I tried to clear out some old snapshots).
> 
> Can one of the developers confirm if the upgrade enables quota?  If so, I will file a bug to ensure the user gets notified/alerted quotas will be enabled (so it can be disabled if necessary).
> 
> -Ron

LXD enables btrfs quota on any newly created btrfs pool, which includes
all your existing ones when upgrading to LXD 2.9 or higher (as the
upgrade step effectively creates a new pool).

That's done so that the size limit feature of LXD can work on btrfs.


Given the potential performance impact and the fact that btrfs quotas
aren't that great to begin with, I'd be fine with adding a pool
configuration option that lets you turn them off. And tweaking our
upgrade code to set that property based on the existing state.


Filing a github issue would be good. Please include what I wrote above
and I suspect Christian will take a look into this shortly.

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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