[pve-devel] Snapshot questions
dietmar at proxmox.com
Mon Sep 7 10:44:23 CEST 2015
> > we
> > want to use it with LXC containers:
> > https://git.proxmox.com/?p=pve-container.git;a=summary
> > Above container management toolkit 'pct' already supports drbd, and it would
> > be really cool to have snapshots, so that we can make snapshot and
> > snapshot backups ;-)
> The same should be easily possible for KVM, too.
Yes, but we do not need that for KVM backup purposes, because we have
a better method with KVM.
> > But that code is quite new, so I would start with qemu, and implement those
> > advanced features later.
> Hmmm, I'm not sure where qemu comes in, when implementing snapshots for
> > > While the Thin LVM
> > > snapshots that DRBDmanage uses might be addressable locally, accessing
> > > them is not recommended. Is that just for information purposes in the GUI?
> > We want to access them when making container backups. I think this should
> > work with dm-thin - why not?
> Because _directly_ accessing them might change the data within them (at
> least replay the filesystem journal).
> The use case we thought of is
> 1) install a VM
> 2) make a snapshot
> 3) use that snapshot as template for new VMs
> That's similar to what docker does.
> Now, if after (2) the snapshot data gets modified, the VMs created via (3)
> might be different from each other (in unexpected ways, ie. the hostname,
> ip, etc. _should_ be different - but other data not), which might then
> cause support overhead.
We do not want to modify the snapshot. We only want read-only access.
> In Cinder the workflow is to create a new volume from a snapshot, even if
> it's just being looked at ... so all the machines in (3) would have the
> same (unmodified) snapshot as base.
> > We can extend the storage API with 'activate_snapshot_volume()' and
> > 'deactivate_snapshot_volume()' if required?
> Well, perhaps.
> Would that make the snapshot itself available for access?
there must be a way toö access snapshot data - else we cannot
(obviously) make a snapshot backup. It is up to the storage driver to
> What if the
> snapshot data is accessible only on another node and not on the current
Well, the storage driver needs to solve that problem...
> >> - but using a snapshot for a new ("clean") VM isn't being done, right?
More information about the pve-devel