[pve-devel] [PATCH 5/5] DRBD: Implement snapshots.

Dietmar Maurer dietmar at proxmox.com
Thu Oct 15 09:25:16 CEST 2015

>  * There's no implementation for volume_snapshot_rollback() yet.
>    Is there a way to change the volume name on rollback?
>    The problem is that DRBDmanage (as of now) won't allow to _replace_
>    the current contents with the ones from the snapshot --
>    but perhaps we want to implement that at some time.

You just need to make sure your plugin return the correct path. The
current code is:

sub filesystem_path {
    my ($class, $scfg, $volname, $snapname) = @_;

    die "drbd snapshot is not implemented\n" if defined($snapname);

    my ($vtype, $name, $vmid) = $class->parse_volname($volname);

    # fixme: always use volid 0?
    my $path = "/dev/drbd/by-res/$volname/0";

    return wantarray ? ($path, $vmid, $vtype) : $path;

>  * For volume_has_feature(), what's the difference between "current" and 
>    "snap" etc.?
>       +        snapshot => { current => 1, snap => 1},

current => 1: You can create a snapshot of currently active volume
snap => 1: You can create a snapshot of a snapshot

AFAIK some storage types allows to create a "snapshot of a snapshot", but
I think we do not use that anywhere. So you can safely ignore that for now
and use

 snapshot => { current => 1 }

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