[ovirt-users] actual size greater than virtual size?

[Nir Soffer]

On Tue, Feb 14, 2017 at 12:07 AM, Gianluca Cecchi <gianluca.cecchi at gmail.com
> wrote:

> Hello,
> I'm on 4.1 with 2 FC SAN storage domains and testing live migration of
> disk.
>
> I started with a CentOS 7.3 VM with a thin provisioned disk of 30Gb.
> It seems that I can see actual disk size in VM--> Snapshots--> Active VM
> line and the right sub pane.
> If I remember correctly before the live storage migration the actual size
> was 16Gb.
> But after the migration it shows actual size greater than virtual (33Gb)??
>

Hi Gianluca,

This is possible for thin disks.

With thin disk we have some overhead for qcow2 metadata, which can be
up to 10% in the worst case. So when doing operations on thin disk, we
may enlarge it to the virtual size * 1.1, which is 33G for 30G disk.

Can you share the output of this commands?

(If the vm is running, you should skip the lvchange commands)

lvchange -ay 5ed04196-87f1-480e-9fee-9dd450a3b53b/9af3574d-dc83-485f-b906-
0970ad09b660he

qemu-img check /dev/5ed04196-87f1-480e-9fee-9dd450a3b53b/
9af3574d-dc83-485f-b906-0970ad09b660he

lvchange -an 5ed04196-87f1-480e-9fee-9dd450a3b53b/9af3574d-dc83-485f-b906-
0970ad09b660he

Nir


> There are no snapshots on the VM right now.
> Is this true? In case could it depend on temporary snapshots done by th
> esystem for storage migration? But in this case does it mean that a live
> merge generates a biggest image at the end..?
>
> The command I saw during conversion was:
>
> vdsm     17197  2707  3 22:39 ?        00:00:01 /usr/bin/qemu-img convert
> -p -t none -T none -f qcow2 /rhev/data-center/mnt/blockSD/
> 922b5269-ab56-4c4d-838f-49d33427e2ab/images/6af3dfe5-
> 6da7-48e3-9eb0-1e9596aca9d3/9af3574d-dc83-485f-b906-0970ad09b660 -O qcow2
> -o compat=1.1 /rhev/data-center/mnt/blockSD/5ed04196-87f1-480e-9fee-
> 9dd450a3b53b/images/6af3dfe5-6da7-48e3-9eb0-1e9596aca9d3/
> 9af3574d-dc83-485f-b906-0970ad09b660he
>
> See currenti situation here:
> https://drive.google.com/file/d/0BwoPbcrMv8mvMnhib2NCQlJfRVE/
> view?usp=sharing
>
> thanks for clarification,
> Gianluca
>
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