Re: [libvirt] Changing the default for qcow2 creation
On Tue, Oct 26, 2010 at 02:11:22AM +1100, Justin Clift wrote:
On 10/26/2010 01:06 AM, Richard W.M. Jones wrote:
<snip>
>> 4. A metadata preallocated qcow2 file: 14.5 seconds
>> qemu-img create -f qcow2 -o preallocated=metadata test.img 300M
Just tested this on a F13 host, and it didn't like the the preallocated
option:
$ qemu-img create -f qcow2 -o preallocated=metadata testvm.qcow2 20G
Unknown option 'preallocated'
qemu-img: Invalid options for file format 'qcow2'.
$
Looks like we'd need to add some kind of testing for the capability
first. :)
The option should be '-o preallocation=metadata'. This works for me
on Fedora 13 too.
This option was introduced to qemu upstream in
commit a35e1c177debb01240243bd656caca302410d38c (Aug 17 2009).
You could actually detect this at runtime by running:
$ qemu-img create -f qcow2 -o preallocation=metadata /dev/null 1M
Formatting '/dev/null', fmt=qcow2 size=1048576 encryption=off cluster_size=0
preallocation='metadata'
$ echo $?
0
$ qemu-img create -f qcow2 -o preallocation=foobar /dev/null 1M
Formatting '/dev/null', fmt=qcow2 size=1048576 encryption=off cluster_size=0
preallocation='foobar'
Invalid preallocation mode: 'foobar'
qemu-img: Error while formatting
$ echo $?
1
However the first command segfaults on Fedora 14 (so near and yet so
far!) I'm going to file a bug about that.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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