[libvirt-users] how to get disk snapshot size

[Kashyap Chamarthy]

On Mon, Mar 16, 2015 at 10:51:21AM +0100, Kashyap Chamarthy wrote:
> On Sun, Mar 15, 2015 at 10:28:30PM +0800, Yitao Jiang wrote:
> > Hi,guys
> > I wanna to get the disk snapshot size, but found nothing libvirt commands
> > related,except qemu-img.
> > I create two disk snapshots, but nothing return its' size
> 
> The below does not seem like snapshots. 

s/not seem like snapshots/not seem like disk snapshots

And, by "The below" I was referring to your output from the original
email (not what I wrote). 

>
> They're *internal* qcow2
> snapshots (original and delta are on the same file).
> 
> A quick example of disk snapshots:
> 
> List the current active device:
> 
>   $ virsh domblklist cirrvm
>   Target     Source
>   ------------------------------------------------
>   hda        /var/lib/libvirt/images/cirros-0.3.3-x86_64-disk.img
> 
> Create a 'disk-only' external snapshot:
> 
>   $ virsh snapshot-create-as --domain cirrvm snap1 \
>         --diskspec vda,file=/export/vmimages/sn1.qcow2 \
>         --disk-only --atomic 
>   
> List again the current active block device:
> 
>   $ virsh domblklist cirrvm
>   Target     Source
>   ------------------------------------------------
>   hda        /export/vmimages/sn1.qcow2
> 
> Get info about the disks involved:
> 
>   $ qemu-img info --backing-chain /export/vmimages/sn1.qcow2
>   image: /export/vmimages/sn1.qcow2
>   file format: qcow2
>   virtual size: 39M (41126400 bytes)
>   disk size: 196K
>   cluster_size: 65536
>   backing file: /var/lib/libvirt/images/cirros-0.3.3-x86_64-disk.img
>   backing file format: qcow2
>   Format specific information:
>       compat: 1.1
>       lazy refcounts: false
>   
>   image: /var/lib/libvirt/images/cirros-0.3.3-x86_64-disk.img
>   file format: qcow2
>   virtual size: 39M (41126400 bytes)
>   disk size: 14M
>   cluster_size: 65536
>   Format specific information:
>       compat: 0.10
> 
> -- 
> /kashyap
> 
> > [root at cskvm01 qcow2]# qemu-img info
> >  /mnt/e6758700-af68-3c06-ade3-53f5f9b93507/e2cf6551-0d2c-4382-a86c-8ba633954ff2
> > image:
> > /mnt/e6758700-af68-3c06-ade3-53f5f9b93507/e2cf6551-0d2c-4382-a86c-8ba633954ff2
> > file format: qcow2
> > virtual size: 5.0G (5368709120 bytes)
> > disk size: 1.0G
> > cluster_size: 65536
> > Snapshot list:
> > ID        TAG                 VM SIZE                DATE       VM CLOCK
> > 1         4fc42d73-8257-42bd-8807-81700fd3c689      0 2015-03-15 21:05:55
> > 01:05:53.583
> > 2         2fd6aeab-cb26-446d-b1c6-e8d70d33f651      0 2015-03-15 21:50:35
> > 00:00:00.000
> > 
> > After wrote data to the disk, then create another snapshot
> > [root at cskvm01 qcow2]# qemu-img info
> >  /mnt/e6758700-af68-3c06-ade3-53f5f9b93507/e2cf6551-0d2c-4382-a86c-8ba633954ff2
> > image:
> > /mnt/e6758700-af68-3c06-ade3-53f5f9b93507/e2cf6551-0d2c-4382-a86c-8ba633954ff2
> > file format: qcow2
> > virtual size: 5.0G (5368709120 bytes)
> > disk size: 3.9G
> > cluster_size: 65536
> > Snapshot list:
> > ID        TAG                 VM SIZE                DATE       VM CLOCK
> > 1         4fc42d73-8257-42bd-8807-81700fd3c689      0 2015-03-15 21:05:55
> > 01:05:53.583
> > 2         2fd6aeab-cb26-446d-b1c6-e8d70d33f651      0 2015-03-15 21:50:35
> > 00:00:00.000
> > 3         63815565-3a06-4366-a1b3-bfeb9c4a07b4      0 2015-03-15 22:22:43
> > 00:00:00.000
> > 
> > VM SIZE column still show 0
> > 
> > Here is my environment
> > qemu-img version 0.12.1, Copyright (c) 2004-2008 Fabrice Bellard
> > libvirtd (libvirt) 0.10.2
> > CentOS release 6.5 (Final) 2.6.32-431.el6.x86_64
> > 
 
-- 
/kashyap