Hi, I'm trying to find out which qcow2 options could be inherited to snapshot/blockcopy and then test them. From https://github.com/qemu/qemu/blob/master/qapi/block-core.json#L4720 we can know all the qcow2 options. As far as I know, size, cluster_size and extended-l2 have already been implemented. So I'm curious that: 1) What are the current status and future plans of other options? Like compat option.

2) Also whether the vol-clone can cover all options?

Thank you very much. And please help to correct me if I have something wrong. Best Regards, Meina Li

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.

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@whitehole ~]# virsh vol-create-as default zzz.qcow2 1G --format > qcow2 > Vol zzz.qcow2 created > > [root@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@whitehole ~]# file /var/lib/libvirt/images/zzz.qcow2 > /var/lib/libvirt/images/zzz.qcow2: QEMU QCOW2 Image (v2), 1073741824 > bytes > > # snapshot creation > [root@whitehole ~]# virsh snapshot-create-as zzz --name zsnap1 > --disk-only > Domain snapshot zsnap1 created > > [root@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@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?