[libvirt-users] move VM disk images between storage pools on the same host

[Paul Raines]

I could not figure out exactly what vol-download or vol-upload do or how
they work. But I did
discover that vol-create-from does work across pools.  It does requires one
to create an XML
def for the volume which I had never done.  It appears at least one does
not have to a give a
complete definition (I did not specify key or extents for example) or even
correct (I specificed
qcow2 format but it still made a raw format volume on the LV).  SO
essentially I did

  virsh vol-dumpxml surfer-2.img vmback > surfer.xml

Edit surfer.xml to have no key, change name, have LV path, etc.

  virsh vol-create-from vmpool1 surfer.xml surfer-2.img --inputpool vmback

I then fired up virt-manager and edited the domain definition to delete the
old disk and add
the new volume as its new disk.  Then booted it in single user mode so I
could fix the
mac address in the ifcfg-eth0 and udev/rules.d/70-persistant-net.rules
files.

On Wed, Nov 7, 2012 at 5:18 PM, Paul Raines <paul.raines at gmail.com> wrote:

> Can you show me how one would use vol-download and vol-upload to do this?
> I cannot figure it out from the docs.  What I have in the old directory
> based storage pool is:
>
> virsh # pool-info vmback
> Name:           vmback
> UUID:           7a8ab88b-42a9-f4c9-128e-83adea324b9a
> State:          running
> Persistent:     yes
> Autostart:      yes
> Capacity:       885.88 GB
> Allocation:     65.57 GB
> Available:      820.31 GB
>
> virsh # vol-list vmback
> Name                 Path
> -----------------------------------------
> lost+found           /vmback/lost+found
> pool.xml             /vmback/pool.xml
> ruby.img             /vmback/ruby.img
> surfer-1.img         /vmback/surfer-1.img
> webtemplate.img      /vmback/webtemplate.img
>
> The new one (LVM) is:
>
> virsh # pool-info vmpool1
> Name:           vmpool1
> UUID:           a95f6f30-b035-7750-6b7d-77953ee7d9af
> State:          running
> Persistent:     yes
> Autostart:      yes
> Capacity:       1.76 TB
> Allocation:     0.00
> Available:      1.76 TB
>
> And I want to move the ruby domain (single disk file ruby.img) to it.
>
>
> On Wed, Nov 7, 2012 at 4:37 PM, Eric Blake <eblake at redhat.com> wrote:
>
>> On 11/07/2012 02:13 PM, Paul Raines wrote:
>> >
>> > I created a new LVM type storage pool on my server and would like to
>> > move my VM disk volumes in a directory-based pool into this new pool.
>> > But I cannot figure out how that is done.  I find plenty of information
>> > on how to migrate live VM images from one host to another, but not on
>> > how to just move one live from one storage pool to another on the same
>> > host.
>> >
>> > If it cannot be done live, how an I do it non-live?  I guess non-live I
>> > could clone, but that would change the MAC address.  Just seems that if
>> > libvirt
>> > can migrate live it should be able to move a VM between storage pools
>> > on the same host even easier.
>>
>> Hmm - you have a good point - right now, 'virsh vol-create-from' and
>> 'virsh vol-clone' only allow motion within a single pool, and not from
>> one pool to another.  I guess you could use 'virsh vol-download' and
>> 'virsh vol-upload' to move volumes from one place to another, although
>> those APIs still lack the ability to cleanly state whether you are
>> migrating metadata (what the host sees) or contents for conversion into
>> a different format (what the guest sees).  At any rate, these commands
>> would be useful on offline disks (and NOT for a disk image in active
>> read-write use by any qemu guest).  I think there's a lot of work that
>> could be done to improve matters with how we manage volumes and pools.
>>
>> Meanwhile, live storage migration IS possible, with libvirt 1.0.0 (now
>> out) and qemu 1.3 (which will be released in December, or if you are
>> comfortable building from qemu.git now), via the 'virsh blockcopy'
>> command.
>>
>>
>>
>
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