libvirt users - Nov 2012 - error: argument unsupported: unable to handle disk requests in snapshot

Hello, a problem occurred during making a snapshot for a guest, ask for help...

1. the xml for snapshotdomain like this:
# cat deployment.1 
<domainsnapshot>
   <name>a</name>
   <disks>
    <disk name='/home/qcow2/disk.0'>
      <driver type='qcow2'/>
      <source file='/home/qcow2/disk.3'/>
    </disk>
  </disks>
</domainsnapshot>

2. when i execute the command , a mistake occurred:
# virsh snapshot-create qcow2 deployment.1
error: argument unsupported: unable to handle disk requests in snapshot 

3. i add the parameter '--disk-only', another mistake occurred:
# virsh snapshot-create qcow2 deployment.1 --disk-only 
error: Failed to take snapshot: unknown command: 'snapshot_blkdev' 

4. my libvirtd version is 0.9.4 , i update to 1.0.0 , also had this problem
# libvirtd --version
libvirtd (libvirt) 1.0.0

5. this is my guest below:
# ls -l
-rw-r--r--  1 oneadmin oneadmin       1540 2012-11-27 15:27 deployment.0
-rw-r--r--  1 root     root            204 2012-11-27 21:28 deployment.1
-rw-r--r--  1 root     root     5772345344 2012-11-28 17:42 disk.0
-rw-r--r--  1 root     root         459264 2012-11-27 21:02 disk.1
-rw-r--r--  1 root     root         372736 2012-11-27 15:25 disk.2

# virsh list
 Id    ???Q                         ???B
----------------------------------------------------
 1     qcow2                          running

# qemu-img info disk.0
image: disk.0
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 5.4G
cluster_size: 65536
Snapshot list:
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         1354019482             142M 2012-11-27 20:31:22   00:00:08.971

is there anyone has the same problem with me ? 




?????? |  ????
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> Hello, a problem occurred during making a snapshot for a guest, ask
> for help...
> 
> 1. the xml for snapshotdomain like this:
> # cat deployment.1
> <domainsnapshot>
>    <name>a</name>
>    <disks>
>     <disk name='/home/qcow2/disk.0'>
>       <driver type='qcow2'/>
>       <source file='/home/qcow2/disk.3'/>
>     </disk>
This says that you want to create an external snapshot...
>   </disks>
> </domainsnapshot>
> 
> 2. when i execute the command , a mistake occurred:
> # virsh snapshot-create qcow2 deployment.1
But this did not request the --disk-only flag, and was not executed
with (unreleased) libvirt 1.0.1.  Older libvirt doesn't support
external snapshots without the --disk-only flag (but the next
release will; assuming that you have new enough qemu).
> error: argument unsupported: unable to handle disk requests in
> snapshot
> 
> 3. i add the parameter '--disk-only', another mistake occurred:
> # virsh snapshot-create qcow2 deployment.1 --disk-only
> error: Failed to take snapshot: unknown command: 'snapshot_blkdev'
This says your qemu is too old.  External snapshots were not possible
until upstream qemu 1.2; it is also available if you use RHEV 3.0
from Red Hat (but NOT if you use RHEL 6.3).
> is there anyone has the same problem with me ?
Yes, since you are trying code that hasn't been implemented
for the versions of software you have installed.
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