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@gmail.com> 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 :|