Re: Is it normal to get bigger qcow2 image after blockcopy?

[Han Han]

On Tue, Nov 7, 2023 at 5:56 AM Nir Soffer <nsoffer@redhat.com> wrote:

On Fri, Nov 3, 2023 at 3:25 AM Fangge Jin <fjin@redhat.com> wrote:

On Thu, Nov 2, 2023 at 5:13 PM Fangge Jin <fjin@redhat.com> wrote:

Recently, I found that the disk size of qcow2 image get bigger(from 6.16G to 8G in my test) after blockcopy.🔄  ❓🔄  ❓

Sorry, it should be "from 6.16G to 6.64G in my test"here

I'm not sure whether this is normal or not. Please help to check. Thanks.🔄  ❓🔄  ❓

Before blockcopy, check source image:🔄  ❓ 

  # qemu-img info -U /var/lib/avocado/data/avocado-vt/images/jeos-27-x86_64.qcow2🔄  ❓

Was this a compressed qcow2 image when you started? maybe you started with an appliance image?

Hi, Nir, I have a question here: How to check if a qcow2 image is compressed?

these are typically compressed. When data is modified, new clusters are stored uncompressed, but data

that was never modified on the original disk remains compressed.

 

After blockcopy, check target image:🔄  ❓

  # qemu-img info -U /var/lib/avocado/data/avocado-vt/images/copy.qcow2 🔄  ❓

This image is not compressed based on the following qmp commands from libvirt log.

The qcow2 file /var/lib/avocado/data/avocado-vt/images/copy.qcow2 is created without compress options, while the

qemu-img info for it shows `compression type: zlib`. Is that mean the image is compressed as well?

 

Qemu command line:🔄  ❓

  -blockdev '{"driver":"file","filename":"/var/lib/avocado/data/avocado-vt/images/jeos-27-x86_64.qcow2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \🔄  ❓
  -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"qcow2","file":"libvirt-1-storage","backing":null}' \🔄  ❓
  -device '{"driver":"virtio-blk-pci","bus":"pci.4","addr":"0x0","drive":"libvirt-1-format","id":"virtio-disk0","bootindex":1}' \🔄  ❓

Qemu monitor command grepped from libvirt log:🔄  ❓
  {"execute":"blockdev-add","arguments":{"driver":"file","filename":"/var/lib/avocado/data/avocado-vt/images/copy.qcow2","node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"},"id":"libvirt-429"}🔄  ❓
  {"execute":"blockdev-create","arguments":{"job-id":"create-libvirt-2-format","options":{"driver":"qcow2","file":"libvirt-2-storage","size":10737418240,"cluster-size":65536}},"id":"libvirt-430"}🔄  ❓
  {"execute":"job-dismiss","arguments":{"id":"create-libvirt-2-format"},"id":"libvirt-432"}🔄  ❓
  {"execute":"blockdev-add","arguments":{"node-name":"libvirt-2-format","read-only":false,"driver":"qcow2","file":"libvirt-2-storage","backing":null},"id":"libvirt-433"}🔄  ❓
  {"execute":"blockdev-mirror","arguments":{"job-id":"copy-vda-libvirt-1-format","device":"libvirt-1-format","target":"libvirt-2-format","sync":"full","auto-finalize":true,"auto-dismiss":false},"id":"libvirt-434"}🔄  ❓
  {"execute":"transaction","arguments":{"actions":[{"type":"block-dirty-bitmap-add","data":{"node":"libvirt-2-format","name":"libvirt-tmp-activewrite","persistent":false,"disabled":false}}]},"id":"libvirt-443"}🔄  ❓
  {"execute":"job-complete","arguments":{"id":"copy-vda-libvirt-1-format"},"id":"libvirt-444"}🔄  ❓

 Nir