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From "Mice Xia" <mice_...@tcloudcomputing.com>
Subject Re: [Discuss] VM Snapshot
Date Wed, 08 Aug 2012 11:59:39 GMT
Hi Tamas,

Thanks for your suggestion.

[quote]
We should not allow this due to the fact one VM's snapshot cannot have any impact on another
VM's snapshot. VM 'B' cannot have volume changes because I rolled back on VM "A".
[/quote]

Actually rollback A will not impact B's attached volume. technically, they are two separate
nodes in disk chain for both xenserver and vmware (for KVM, i have no idea)

For usage problem, we can make usage server think the volume in quesiton is deleted, though
the capacity is not fully released due to its parent node still exists. This might be a problem
and maybe we need to charge their snapshot usage.

Though they are not showstoppers, I'm inclined to agree with you. I tend to implement this
in an incremental approach, firstly make it happen, then make it better with feedbacks from
community and end users.

Regards
Mice

-----Original Message-----
From: Tamas Monos [mailto:tamasm@veber.co.uk]
Sent: 2012-8-8 (ζ˜ŸζœŸδΈ‰) 18:50
To: cloudstack-dev@incubator.apache.org
Subject: RE: [Discuss] VM Snapshot
 
Hi,

a) 'vm snapshot, detach volume and attach it to another VM, rollback snapshot'
2, allow to snapshot/rollback, for a), this will result in two volumes, one attached to anther
VM, one attached to VM that rollback from snapshot;
We should not allow this due to the fact one VM's snapshot cannot have any impact on another
VM's snapshot. VM 'B' cannot have volume changes because I rolled back on VM "A".

b) 'vm snapshot, detach and destroy volume, rollback snapshot'
2) allow to snapshot/rollback, for b), destroyed volume is not truly expunged and capacity
is not released
This will lead to usage problems. The customer will complain he has deleted his volumes but
still getting charged for it, yes because cloud-usage will still see the volume and report
it in usage records.

My suggestion would be 1) disallow detach volumes if specified VM has VM snapshots. The end
user can always add more but cannot remove once snapshotted. The end user must remove snapshots
before wants to remove volumes.
Also all snapshots created after the one I reverted to should be invalidated and deleted/expunged.
I know this would cripple the snapshot functionality quite a bit but for now I think would
work perfectly, without making fundamental changes to CS infrastructure and would allow us
to have proper snapshots and not exported templates.


Regards

Tamas Monos                                               DDI         +44(0)2034687012
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