[ovirt-users] Storage migration: Preallocation forced on destination

[Nicolás]

El 04/03/16 a las 20:23, Nir Soffer escribió:
> On Fri, Mar 4, 2016 at 7:07 PM, Nicolás <nicolas at devels.es> wrote:
>> Hi,
>>
>> We're migrating an existing storage (glusterfs) to a new one (iSCSI). All
>> disks on glusterfs are thin provisioned, but when migrating to iSCSI the
>> following warning is shown:
>>
>>      The following disks will become preallocated, and may consume
>> considerably more space on the target: local-disk
>>
>> Why is that? Is there a way to migrate disks so they are thin provisioned on
>> iSCSI as well?
> The issue is that we use raw sparse format for thin provisioned disks
> on file based
> storage. The file system provides the thin provisioning, maintaining holes in
> the files.
>
> When we create the destination lv, we use the disk virtual size, so you get
> practically a preallocated volume.
>
> I think we can do better - before copying the disk, we can check the actual used
> space (e.g. what qemu-img info or stat report), and create the
> destination lv using
> the used size (plus additional space for qcow format).
>
> I tested this by extending the destination lv manually and then
> copying data manually
> using qemu-img convert, and it works.
>
> Can you file a bug for this, and explain the use case?
>
> Nir

Done, for the ones interested on it: 
https://bugzilla.redhat.com/show_bug.cgi?id=1314959

Thanks.

Regards.