[pve-devel] [PATCH v3 qemu-server 11/11] qcow2: add external snapshot support

[DERUMIER, Alexandre]

>>out of curiosity, besides the obvious cases where external snapshots 
>>would be useful, i.e. on raw files and on lvm (not lvm-thin), what
>>other 
>>cases would be useful given that they already have snapshot support 
>>(qcow2 with the internal one, zfs, btrfs, lvm-thin etc)?

>>not having it on raw files I think would take away a lot of its 
>>usefulness, but I could be wrong if there are uses I can't imagine, 
>>maybe make something more possible with replicas and migrations? (I 
>>haven't looked into it enough)

I think they could be use for remote replication with snapshot
export/import if storage don't support it  (lvm-thin for example).

I'm planning to add pseudo-thin provisoniong too on lvm shared block.
(lvm smaller than the qcow2 format, with dynamic lvm size increase
through  a proxmox special daemon )



Note that , for .raw support, it's still possible to add support later,
if user really want it.

Just keep it simple for a first version then add more feature over time
:)


Also, the target is really network storage (qcow2 on nfs/cifs , lvm +
qcow2 on SAN block), that's why I think that network latency also hide
the perf difference between qcow2 && raw.

For local storage, with super fast nvme, it don't make too much sense
to use qcow2. you can use zfs, lvm-thin,.. where internal snasphots are
working great :)