[zfs-discuss] [RFC] Improved versioned pointer algorithms

Daniel Phillips
Mon, 14 Jul 2008 23:01:19 -0000

On Monday 14 July 2008 08:29, Akhilesh Mritunjai wrote:
> Still reading, but would like to correct one point.
>
> > * It would seem that ZFS is deeply wedded to the
> > concept of a single,
> > linear chain of snapshots.  No snapshots of
> > snapshots, apparently.
> >    http://blogs.sun.com/ahrens/entry/is_it_magic
>
> Writable snapshots are called "clones" in zfs. So infact, you
have trees of snapshots and clones. Snapshots are read-only, and you can create
any number of "writable" clones from a snapshot, that behave like a
normal filesystem and you can again take snapshots of the clones.

Thanks for clarifying Akhilesh.

That was not clear from the blog link above, which says that any blocks in
a deleted snapshot born after the most recent snapshot will be freed.  I do not
see how that works for clones of snapshots.  Are the details of clone deletion
covered anywhere, or did I just not read the blog closely enough?

Regards,

Daniel