On Wed, Aug 10, 2011 at 10:02:41AM -0400, Dave Allan wrote: > On Wed, Aug 10, 2011 at 10:20:10AM +0100, Daniel P. Berrange wrote: > > On Tue, Aug 09, 2011 at 03:28:50PM -0700, Yih-Herng Chuang wrote: > > > > > > > > > Seems like different libvirt versions generate a storage volume name in > > > different format. We would like to learn how libvirt names a storage > > > volume under a block based storage pool. So that we may properly extract > > > the LUN identifier out of the volume name for now and in the future. > > > > > > On host A loaded with libvirt 0.8.7 > > > # virsh vol-list SanPool1 > > > Name Path > > > ----------------------------------------- > > > unit:0:0:11 /dev/disk/by-id/wwn-0x600a0b800013071a000035ec4e32b832 > > > > This is the new naming scheme which we plan to stick with long > > term. The key point of the naming scheme is that the name is > > stable across reboots, and across login/logout of iSCSI targets. > > > > > > > > On host B loaded with libvirt 0.8.1 > > > > > > # virsh vol-list SanPool1 > > > Name Path > > > ----------------------------------------- > > > 1.0.0.0 /dev/disk/by-id/wwn-0x60080e500017e1d40000d0b74d873b13 > > > > This was the old method, which was broken, because we should not > > have been including the HBA number in the name (the leading '1' > > here). The HBA number changes every time you login to an iSCSI > > target, or everytime an NPIV HBA is created, so it resulted in > > an unstable name which changed frequently > > Since I was the one who came up with the original naming method, I > should probably chime in. Note that although the HBA number changes > rapidly with iSCSI and NPIV, resulting as Dan points out in unstable > volume names, the other parts of the tuple are not guaranteed to > remain stable, either. Changes to SAN topology will result in volume > name changes. The only identifier you can depend on is the UUID of > the logical unit. More specifically - path: assuming use of /dev/disk/by-id paths, this should be globally unique and stable across OS reboots & for all hosts with the pool configured in the same way. - name: this is unique within the scope of the storage pool, and is stable across hosts & reboots, provided the storage topology is not changed. - key: this is globally unique across all pools and all OS no matter what configuration is used. For the latter, we use a number of strategies. For LVM we use the LVM volume UUID, while for SCSI/iSCSI we use the SCSI lun's WWN Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
