On Thu, Oct 7, 2010 at 6:39 AM, Francis Galiegue <fgalie...@gmail.com> wrote:
> While I fully understand (and use) the purpose of snapshots, I don't
> quite fathom the use case for subvolumes, apart from btrfs-convert...
> Why has btrfs grown such a feature in the first place? Can someone
> give me a use case for them?

I'm new here; I trust that someone will correct me if wrong:

As I understand it, since snapshotting works on volumes, having
subvolumes allows a smaller thing that you can take a snapshot of. A
use case? One could give each user on a multi-user system their own
subvolume rather than their own directory, under /home/... and then
take snapshots of these home directories to implement regular backups
(1)without duplicating unchanged files and (2) with independence
between the users.

As to why they exist, I understand that they began as an
implementation detail of snapshots, rather than their creation having
been driven by the needs of a particular use case, and one could
legitimately criticize currently offered use cases (such as the one
above) as contrived.

I believe it is fair to consider a new subvolume as equivalent of a
snapshot of an empty file system.
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