[Gluster-users] [Gluster-devel] User-serviceable snapshots design

[Anand Avati]

On Thu, May 8, 2014 at 11:48 AM, Jeff Darcy <jdarcy at redhat.com> wrote:

> > client graph is not dynamically modified. the snapview-client and
> > protocol/server are inserted by volgen and no further changes are made on
> > the client side. I believe Anand was referring to " Adding a
> protocol/client
> > instance to connect to protocol/server at the daemon" as an action being
> > performed by volgen.
>
> OK, so let's say we create a new volfile including connections for a
> snapshot
> that didn't even exist when the client first mounted.  Are you saying we do
> a full graph switch to that new volfile?


No graph changes either on client side or server side. The snap-view-server
will detect availability of new snapshot from glusterd, and will spin up a
new glfs_t for the corresponding snap, and start returning new list of
"names" in readdir(), etc.


>  That still seems dynamic.  Doesn't
> that still mean we need to account for USS state when we regenerate the
> next volfile after an add-brick (for example)?  One way or another the
> graph's going to change, which creates a lot of state-management issues.
>

No volfile/graph changes at all. Creation/removal of snapshots is handled
in the form of a dynamic list of glfs_t's on the server side.
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