[Question] Which qcow2 options could be inherited to snapshot/blockcopy?

[Gionatan Danti]

Il 2022-11-26 10:36 Gionatan Danti ha scritto:
> Il 2022-11-21 10:30 Peter Krempa ha scritto:
>> In regards to the 'compat' option in terms of snapshots/blockcopy, we
>> don't set it and thus use the qemu default. Since both operations 
>> create
>> a new image with an existing qemu instance, the default new qemu 
>> format
>> is okay.
> 
> Hi, some idea on why creating a qcow2 volume and snapshotting it via a
> backing file results in two qcow2 files with different format (v2 vs
> v3)? Example below:
> 
> # volume creation
> [root at whitehole ~]# virsh vol-create-as default zzz.qcow2 1G --format 
> qcow2
> Vol zzz.qcow2 created
> 
> [root at whitehole ~]# qemu-img info /var/lib/libvirt/images/zzz.qcow2
> image: /var/lib/libvirt/images/zzz.qcow2
> file format: qcow2
> virtual size: 1 GiB (1073741824 bytes)
> disk size: 16.5 KiB
> cluster_size: 65536
> Format specific information:
>     compat: 0.10
>     compression type: zlib
>     refcount bits: 16
> 
> [root at whitehole ~]# file /var/lib/libvirt/images/zzz.qcow2
> /var/lib/libvirt/images/zzz.qcow2: QEMU QCOW2 Image (v2), 1073741824 
> bytes
> 
> # snapshot creation
> [root at whitehole ~]# virsh snapshot-create-as zzz --name zsnap1 
> --disk-only
> Domain snapshot zsnap1 created
> 
> [root at whitehole ~]# qemu-img info /var/lib/libvirt/images/zzz.zsnap1
> image: /var/lib/libvirt/images/zzz.zsnap1
> file format: qcow2
> virtual size: 1 GiB (1073741824 bytes)
> disk size: 16.5 KiB
> cluster_size: 65536
> backing file: /var/lib/libvirt/images/zzz.qcow2
> backing file format: qcow2
> Format specific information:
>     compat: 1.1
>     compression type: zlib
>     lazy refcounts: false
>     refcount bits: 16
>     corrupt: false
>     extended l2: false
> 
> [root at whitehole ~]# file /var/lib/libvirt/images/zzz.zsnap1
> /var/lib/libvirt/images/zzz.zsnap1: QEMU QCOW2 Image (v3), has backing
> file (path /var/lib/libvirt/images/zzz.qcow2), 1073741824 bytes
> 
> Regards.

Hi all,
anyone with some ideas/suggestions?

Regards.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
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