Re: usrquota

[Martin Walter <mawa@uni-freiburg.de>]

On Fri, Jan 17, 2014 at 06:24:26PM +0000, Duncan wrote:
> Martin Walter posted on Fri, 17 Jan 2014 15:18:41 +0100 as excerpted:
> 
> > Our problem is a zfs with 20,000 quota-enabled homedirectories and 100
> > snapshots.
> > We would really like to do the same with btrfs, but we don't know how to
> > replace the zfs quotas with btrfs subvolume quotas. It seems unfeasible
> > to handle 2,000,000 subvolumes.
> > e.g. we would have to create every hour 20,000 snapshots and delete the
> > same amount.
> > 
> > Is there any chance to get real user quotas with btrfs?
> 
> At present I'd suggest staying away from quotas on btrfs in any case, as 
> there have been some serious bugs (quotas going negative with snapshot 
> deletion, etc) in the way they're tracked.  I don't use quotas here so 
> haven't closely followed status and perhaps the bugs are fixed, but never-
> the-less, it's something I'd recommend staying away from for the time 
> being.  Certainly for usage at that scale.  I'd suggest reexamining that 
> decision perhaps a year from now, but it's simply not ready for that, now.
> 
> So I'd say stick with zfs for quota usage at that scale, for now.
> 
> On a more general note, btrfs is just beginning to stabilize in 
> general... the kernel config warnings were just toned down for 3.13, 
> etc.  However, as mkfs.btrfs warns when you create a btrfs filesystem, 
> it's still not entirely stable.  This year should bring a lot of 
> stabilization as development focus gradually switches from features to 
> stabilization, but again, for production deployment at that scale, I'd 
> suggest waiting a year and reexamining the question.
> 
> Of course you can still do pilot deployments now, but even more than with 
> fully stable filesystems, be sure you have current and tested backups, 
> because it's still possible you'll need to use them.  Also, using the 
> current latest stable kernel (so 3.12.x currently, soon to be 3.13) if 
> not the development kernel is still recommended, as critical fixes still 
> go into every new kernel, and while they're marking more of them for 
> stable now, not all of them reach stable.  Again, the warning was only 
> toned down with 3.13, so from there I'd hope they backport stable fixes, 
> but I wouldn't count on it before that.  And btrfs-tools, while less 
> critical, is kernel-version synced from 3.12 as well, so you want a btrfs-
> tools release at least reasonably comparable to your current kernel (v3.12 
> current and minimum).
> 
> (This as just a user and list regular, not a dev, myself.)

I am actually very happy with btrfs. I use it everywhere, where I need no userquotas.
Unfortunately subvolume quotas are not a real substitute for userquotas.
Hopefully the developers will implement it someday.

In any case, many thanks,
Martin