[pve-devel] Snapshots over DRBD

[Fabian Grünbichler]

On Wed, Jul 27, 2016 at 11:18:42PM +0200, Gilou wrote:
> Hi,
> 
> I just set up a PoC using Proxmox 4.2 & DRBD 9, and realized afterwards
> that I can't snapshot those.
> 
> I remember a discussion about someone working on patching it, but I
> guess it didn't make it through... I see the DRDB cleverly uses
> drbdmanage to set each thin LVM as primary accordingly, would it be
> harder to allow drbd snapshots than local snapshots ?
> 

The problem is that DRBD9 snapshots cannot be rolled back in place (they
can only be restored to a new resource), which breaks all the
assumptions regarding rollbacks in the PVE code base. Allowing the
creation of snapshots without the ability to actually use them is
worthless.

So we either need to wait for drbdmanage to get an option to restore in
place ("rollback"), or we would need to add a lot of workaround code in
the PVE code base. The second is not really a viable option..