Re: [ANNOUNCE] Btrfs: a copy on write, snapshotting FS

Chris Mason
2007-06-13T14:58:48Z

On Wed, Jun 13, 2007 at 10:00:56AM -0400, John Stoffel wrote:
> >>>>> "Chris" == Chris Mason <chris.mason@oracle.com> writes:
> >> As a user of Netapps, having quotas (if only for reporting purposes)
> >> and some way to migrate non-used files to slower/cheaper storage would
> >> be great.
>
> Chris> So far, I'm not planning quotas beyond the subvolume level.
>
> So let me get this straight. Are you saying that quotas would only be
> on the volume level, and for the initial level of sub-volumes below
> that level? Or would *all* sub-volumes have quota support? And does
> that include snapshots as well?

On disk, snapshots and subvolumes are identical...the only difference is
their starting state (sorry, it's confusing, and it doesn't help that I
interchange the terms when describing features).

Every subvolume will have a quota on the number of blocks it can
consume. I haven't yet decided on the best way to account for blocks
that are actually shared between snapshots, but it'll be in there
somehow. So if you wanted to make a snapshot readonly, you just set the
quota to 1 block.

But, I'm not planning on adding a way to say user X in subvolume Y has
quota Z. I'll just be: this subvolume can't get bigger than a given
size. (at least for version 1.0).

-chris