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' In the case of XenAPI there will be no target, it can be '/' for now as you said. The <source> tag will have the host name and path. - App creates a storage volume called 'bar' The volume target path will be /sr-uuid/vol-uuid - Storage pool driver creates a path for volume based on pool target and volume name. eg it might decide /foo/bar driver creates the path /sr-uuid/vol-uuid - App queries path of new volume and gets '/foo/bar' virStorageVolGetPath() will return same as above for any volume - App creates a new disk, passing '/foo/bar' in the <disk> element in the guest XML source in the disk element will have the same path. Here using sr-uuid the driver would locate the actual location of the SR and the specified volume in it using vol-uuid and attach it to the new VM being created.

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.

This will be the UUID path as usual. As I said earlier XenAPI will get the Actual location from the UUIDs and attach with the new guest VM.

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.

There is no pool target so I'll just leave it with '/' for now. |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|