Hi, Alessandro

              I would recommend you to read this article: 
http://support.citrix.com/article/CTX122978 Note parts about "VDI remapping".  
I would probably do this way:  remove all snapshots to be able to coalesce 
VDI-s (look for "Advanced Coalescing Scenarios" chapter). Than CS should see VM 
and their disks with original UUID-s. Then you can create snapshots using CS 
interface.

Vadim.

-----Original Message-----
From: Alessandro Caviglione [mailto:c.alessan...@gmail.com] 
Sent: Saturday, May 23, 2015 3:36 PM
To: users@cloudstack.apache.org
Subject: A little lesson about Snapshots

...so guys, let me tell you my little adventure with snapshots.
Our environment is ACS 4.4.2 with XS6.2SP1.
Yesterday we done some activities on a customer's server, foolishly we have 
XenCenter interface already opened and we took a couple of snapshot during our 
activities.
At the end, we've to change the service offering of the server, so we opened 
ACS web interface, stopped the instance and change service offering.
When we start again the server the instance would not start... in ACS logs we 
see:

Catch Exception
com.xensource.xenapi.Types$UuidInvalid :VDI getByUuid for uuid:
xxxxxxxxx failed due to The uuid you supplied was invalid.

After google a little, we understood that we stopped the instance with a couple 
of active snapshots took from XenCenter instead of ACS.
So... maybe, in ACS db there was a wrong uuid of the Root Disk of the 
instance...
In fact, in "Volume" table of ACS db we see that "path" record for that 
instance was different from the one we see in "xe vdi-list" in XenServer.
So, this was our situation in XenServer:

uuid ( RO)                : 0345bbf9-be9c-45ae-80e7-fa5fff31625b
name-label ( RW): ROOT-136
snapshot-of ( RO): a0de7625-f98a-4443-a13f-6c9577c2d958
snapshot-time ( RO): 20150522T21:20:39Z
sm-config (MRO): vhd-parent: 9ffe5381-5a0e-4e7c-8614-e19318d9dec9


uuid ( RO)                : cf50f4ba-05b9-46f9-85e4-f1ac82cdb6b4
name-label ( RW): ROOT-136
snapshot-of ( RO): a0de7625-f98a-4443-a13f-6c9577c2d958
snapshot-time ( RO): 20150522T12:49:44Z
sm-config (MRO): vhd-parent: 083364dc-b43e-401b-ab73-1959a23a9d1

uuid ( RO)                : a0de7625-f98a-4443-a13f-6c9577c2d958
name-label ( RW): ROOT-136
snapshot-of ( RO): <not in database>
snapshots ( RO): 0345bbf9-be9c-45ae-80e7-fa5fff31625b;
cf50f4ba-05b9-46f9-85e4-f1ac82cdb6b4

Now, I need to understand a couple of things...
First of all... how Snapshots works??
Instinctively we change the "path" record in ACS db with the first one 
(0345bbf9-be9c-45ae-80e7-fa5fff31625b), you can see that snapshot-time is later 
than others.
When instance started we see that was not tha "last situation" of the 
instance... so we stopped again and changed "path" record with the 
"a0de7625-f98a-4443-a13f-6c9577c2d958".
So far so good, now the instance was in the last situation and all works fine!!
Now... why the last situation was in the ROOT DISK that is has not parent 
snapshot?
I thought that last Snapshot ROOT DISK has the last instance situation...

Second... since now the instance is running fine but nor in ACS, nor in 
XenCenter we can see any Snapshot (that in fact there are two), how can we 
delete those Snapshots??

Thank you!!

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