[pve-devel] some news for snapshots

[Alexandre DERUMIER]

Hi,
I have done some tests and send messages to differents mailing,

here some infos:


for qcow2 internal snapshot:
-----------------------------
We can't use qemu-img -c, to create snasphot, when vm is online. (confirmed by Stefan Hajnoczi from qemu mailing)
It cause corruptions, and bad things. (I have tested it and had crashed my qcow2 file after some online snapshot and offline rollback)
So no online internal snapshot for now. (I have tell the question if online internal snapshot is on the roadmap, don't have response yet from qemu mailing)

Offline internal snapshot works fine.

The only way to do this online, is using external snapshot and qmp command.

Another bad thing, currenly to merge snapshots, it's from parent to childen.

So have a 100GB image, take a snapshot, write 300bytes. to merge it, you need to read/write 100GB from parent to child.
Qemu dev are working curently on a way to merge from child to parent.


Sheepdog
--------
I'm working on it too, I have had bugs with 0.4, last git seem to works better, but I don't have the rollback behaviour I expected (see sheepdog mailing)


rbd
---
Works fine, (snapshot/rollback) :)

nexenta
-------
works fine too (snapshot/rollback)