Re: [RFC] about libxl snapshot

[Ian Jackson <Ian.Jackson@eu.citrix.com>]

Bamvor Jian Zhang writes ("[RFC] about libxl snapshot"):
> our plan about snapshot is:
> 1, basic disk snapshot support(internal snapshot, qdisk as backend).
> ALREADY SENT.

Right, see my comments on that.  I'm not sure what feature it
provides, apart from something that could be done with qemku-img.

> 2, vm snapshot(memory save, snapshot the whole snapshot with transaction qmp
> opeartion, only support internal disk snapshot at this step.
> in this step, we plan to add the vm snapshot record in xenstore in domain in
> order to management the status of vm snapshot.

I'm not sure what you mean by "add the vm snapshot record in
xenstore".  I don't know what "vm snapshot record" is exactly.  If you
mean the domain save state it's far too big for xenstore.

> question:
> in GSOC2013, there is a requirement: "Add VM snapshot functionalities to libxl
> save/restore and migration functions". is it mean add a flag to create snapshot
> in save, revert snapshot in restore besides the dedicated vm snapshot command?
> or just implement the snapshot in save, restore and migration?
> it might be more clear for user if there is a dedicated snapshot command.

I agree that a dedicated command might be clearer.  This is a matter
for the implementor to think about and decide in consultation with the
community.  I don't think the 2013 GSOC requirement was intended to
specify an xl UI.

> 3, some "advanced" feature such driver-mirror, support other backend.
> 
> when i prepare to send this out, i found that there is a GSOC project during
> community review this week. i am sorry about i do not send this discussion
> eariler. sorry if i break the plan of xen community.

We welcome contributions from anyone, whether within GSOC or without.
Sadly sometimes that means things come in parallel, which can involve
duplicated work.  We'll know fairly soon which GSOC projects have been
accepted.

Ian.