project quota: df/reservations

[Dave Chinner]

On Fri, Feb 04, 2011 at 01:25:53PM +0100, Jerzy Borkowski wrote:
> Hello,
> 
> 1) Fancy a project with quota set to 10GB, and filled
> with 5GB of data. When I type
> 
>   df /path/to/project/tree
> 
> it shows 5GB free space. Now, the root user
> fills up the disk (outside project tree), so the
> XFS filesystem is really 100% full. The df command
> still shows 5GB free space. I guess, this is
> intentional. I propose to add some switch/flag
> (either during mount or project creation),
> which would tell XFS to report in statfs() calls
> the free space as: min(project_free_space, filesystem_free_space).

If you just run "df" or "df /path/to/mtpt" rather than asking
specifically for the project tree path, you should see the real
filesystem usage.

Think of project quotas like thin provisioned filesystems - they can
still have space available when the underlying storage runs out and
it is up to the admin to manage this situation.

> 2) is there any way to have space reservations for projects (like in ZFS) ?
> For instance, a project with 10GB quota and 7GB of preallocated
> space, so even root, writing outside the project tree, cannot
> completely fill up the disk.

No. Quotas can only be used to limit space usage, not reserve it.
It could probably be done, but it's not a simple retrofit...

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com