If an instance has had an attached volume volume-updated twice in a "round-trip" - ie, volume-update $vol1 $vol2, then volume-update $vol2 $vol1 - it cannot be live-migrated.
(--volume-type iscsi isn't mandatory - in my devstack environment there is no iscsi
volume-type, but that doesn't stop me from reproducing this bug)
2. Boot an instance.
# nova boot --flavor 1 --image $imageid --nic net-id=$netid testvm1
3. Attach one iscsi volume to testvm1.
# nova volume-attach testvm1 $test_vol1
4. Do volume-update to swap volume to 2nd one. (1st time volume-update)
# nova volume-update testvm1 $test_vol1 $test_vol2
5. Do volume-update again to swap volume back to the 1st one. (2nd time volume-update)
# nova volume-update testvm1 $test_vol2 $test_vol1
6. Live migrate instance to other compute node.
# nova live-migration testvm1
Expected result
===============
Live migration succeeds.
Actual result
=============
Live migration fails with:
Apr 27 10:32:14 multi9h-3 nova-compute: File "/usr/lib64/python2.7/site-packages/libvirt.py", line 1939, in migrateToURI3
Apr 27 10:32:14 multi9h-3 nova-compute: if ret == -1: raise libvirtError ('virDomainMigrateToURI3() failed', dom=self)
Apr 27 10:32:14 multi9h-3 nova-compute: libvirtError: missing source information for device vdb
Environment
===========
This has been originally reported [1] in Red Hat OSP 9 (Mitaka) and is reproducible on devstack master as well.
Additional information
======================
There are two things going on here.
1. When performing the volume-update, the libvirt driver calls virDomainBlockRebase without the VIR_DOMAIN_BLOCK_REBASE_COPY_DEV flag [2], meaning the device XML changes from <source dev=/dev/isci/lun> to <source file=/dev/iscsi/lun>. This is a problem because /dev/iscsi/lun isn't a regular file, and causes the above error, except you need the "round-trip" volume-update to trigger it. Why? Because:
2. The serial number isn't updated when doing volume-update, and there's a bit of live-migration code [3] that checks for serial numbers before updating the XML. If the serial numbers don't match, the XML isn't updated, and libvirt doesn't notice that /dev/iscsi/lun isn't a file.
Description
===========
If an instance has had an attached volume volume-updated twice in a "round-trip" - ie, volume-update $vol1 $vol2, then volume-update $vol2 $vol1 - it cannot be live-migrated.
Steps to reproduce
==================
1. Create two iscsi volumes.
# cinder create --name test_vol1 --volume-type iscsi 1
# cinder create --name test_vol2 --volume-type iscsi 1
(--volume-type iscsi isn't mandatory - in my devstack environment there is no iscsi
volume-type, but that doesn't stop me from reproducing this bug)
2. Boot an instance.
# nova boot --flavor 1 --image $imageid --nic net-id=$netid testvm1
3. Attach one iscsi volume to testvm1.
# nova volume-attach testvm1 $test_vol1
4. Do volume-update to swap volume to 2nd one. (1st time volume-update)
# nova volume-update testvm1 $test_vol1 $test_vol2
5. Do volume-update again to swap volume back to the 1st one. (2nd time volume-update)
# nova volume-update testvm1 $test_vol2 $test_vol1
6. Live migrate instance to other compute node.
# nova live-migration testvm1
Expected result
===============
Live migration succeeds.
Actual result
=============
Live migration fails with:
Apr 27 10:32:14 multi9h-3 nova-compute: File "/usr/lib64/ python2. 7/site- packages/ libvirt. py", line 1939, in migrateToURI3
Apr 27 10:32:14 multi9h-3 nova-compute: if ret == -1: raise libvirtError ('virDomainMigr ateToURI3( ) failed', dom=self)
Apr 27 10:32:14 multi9h-3 nova-compute: libvirtError: missing source information for device vdb
Environment
===========
This has been originally reported [1] in Red Hat OSP 9 (Mitaka) and is reproducible on devstack master as well.
Additional information ======= ======= =
=======
There are two things going on here.
1. When performing the volume-update, the libvirt driver calls virDomainBlockR ebase without the VIR_DOMAIN_ BLOCK_REBASE_ COPY_DEV flag [2], meaning the device XML changes from <source dev=/dev/isci/lun> to <source file=/dev/ iscsi/lun> . This is a problem because /dev/iscsi/lun isn't a regular file, and causes the above error, except you need the "round-trip" volume-update to trigger it. Why? Because:
2. The serial number isn't updated when doing volume-update, and there's a bit of live-migration code [3] that checks for serial numbers before updating the XML. If the serial numbers don't match, the XML isn't updated, and libvirt doesn't notice that /dev/iscsi/lun isn't a file.
[1] https:/ /bugzilla. redhat. com/show_ bug.cgi? id=1446446 libvirt. org/html/ libvirt- libvirt- domain. html#virDomainB lockRebase /github. com/openstack/ nova/blob/ master/ nova/virt/ libvirt/ migration. py#L158
[2] http://
[3] https:/