Re: [libvirt] XenAPI remote storage - target path
On Tue, Mar 16, 2010 at 10:16:05AM +0000, Sharadha Prabhakar (3P) wrote:
Hi,
I'm trying to write a Remote Storage driver for XenAPI.
I see that target-path is used for both storage pools and volumes.
In the case of XenAPI remote storage, the storage is not mounted on the
local host where libvirt is running. Storage is maintained in a remote location only.
In this case how do I specify target-path and how do I go about creating
a VM with storage using libvirt APIs with virsh and virt-manager.
Virt-manager expects me to give an absolute path for target-path. But In my case
I don't have an absolute path.
Can I have a target path like this for a particular storage volume
"/storage pool uuid/storage-vol uuid"? This will help me identify which storage
pool is
Libvirt talking about and which volume in it. Using this information I can fetch data
from
The remote location and give it back to libvirt. Is this approach
ok or does libvirt support my specific remote storage case in some way. Could someone
clarify please?
It may help to understand the usage scenario.
- App creates a storage pool with a target '/foo'
- App creates a storage volume called 'bar'
- Storage pool driver creates a path for volume based on pool target and
volume name. eg it might decide /foo/bar
- App queries path of new volume and gets '/foo/bar'
- App creates a new disk, passing '/foo/bar' in the <disk> element in
the guest XML
The real key thing here is that 'virStorageVolGetPath' *must* return a path
suitable for use in the guest XML <disk> element <source file=/foo/bar>
To answer your question then, we ned to know what the path looks like that
you use to configure the guest disk when starting the guest ? Once you
know that, then the storage driver must be implemented such that
virStorageVolGetPath() returns a path that matches what XenAPI wants for
the guest config.
As for pool target, if nothing else you can simply require that the pool
is configured with a target path of '/' at which point it is essentially
ignorable, since all paths start with a '/' anyway.
Regards,
Daniel
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