On Wed, Jan 06, 2021 at 04:36:46PM +0100, Peter Krempa wrote: > On Wed, Jan 06, 2021 at 17:16:24 +0200, Nir Soffer wrote: > > On Wed, Dec 2, 2020 at 4:57 PM Joy Li <joooy.li@xxxxxxxxx> wrote: > > [...] > > > Comparing to state before reboot: > > > > # virsh -r domblklist disk-mapping > > Target Source > > --------------------------------------------------------------------------------------------------------------------------------------------------------------- > > sdc - > > sda /rhev/data-center/mnt/blockSD/84dc4e3c-00fd-4263-84e8-fc246eeee6e9/images/40018b33-2b11-4d10-82e4-604a5b135fb2/40f455c4-8c92-4f8f-91c2-991b0ddfc2f5 > > vda /dev/mapper/3600140594af345ed76d42058f2b1a454 > > vdb /dev/mapper/360014050058f2f8a0474dc7a8a7cc6a5 > > vdc /dev/mapper/36001405b4d0c0b7544d47438b21296ef > > > > # ls -lh /dev/disk/by-id/virtio-* > > lrwxrwxrwx. 1 root root 9 Jan 6 09:42 > > /dev/disk/by-id/virtio-b97e68b2-87ea-45ca-9 -> ../../vda > > lrwxrwxrwx. 1 root root 9 Jan 6 09:42 > > /dev/disk/by-id/virtio-d9a29187-f492-4a0d-a -> ../../vdb > > lrwxrwxrwx. 1 root root 9 Jan 6 09:51 > > /dev/disk/by-id/virtio-e801c2e4-dc2e-4c53-b -> ../../vdc > > > > In the guest disks are mapped to the same device name. > > > > It looks like libivrt domblklist is not correct - vdb and vdc are switched. > > Peter, this expected? > > The names in 'virsh domblklist' are unfortunately and confusingly chosen > to match the expected /dev/ device node name, but it's at kernel's > discretion to name /dev/ nodes. > > This means that it's not guaranteed that what you see in 'virsh > domblklist' will match the state in the guest. Essentially the only thing the disk device name is used for is sorting the <disk> elements within the XML document. This in turn affects what order PCI addresses (virtio-blk) or SCSI LUNS (virtio-scsi) are assigned in. This influences/hints as to what order the guest OS *might* assign device names in. The device name from the XML is not exposed to the guest directly though. Certainly when hotplugging/unplugging is involved all bets are off wrt what disk names you'll see in the guest vs the XML. Dont expect them to match except by luck. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
