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There is an issue in os-brick related to multipath support for iSCSI
connector. Basically when multipathd is configured with feature
'find_multipaths' set to 'yes' #1815844 [0].

In this situation, multipathd automatically generate multipath device
when it discovers:

 - There are at least two non-blacklisted paths with the same WWID.
 - The user manually forces the creation of the device by specifying a
   device with the multipath command.
 - A path has the same WWID as a multipath device that was previously
   created (even if that multipath device does not currently exist).
   Whenever a multipath device is created, multipath remembers the
   WWID of the device so that it will automatically create the device
   again as soon as it sees a path with that WWID.

This situation happens as described in bug #1815844 [0] when we attach
a volume, detach it and then re-attach it again.

  openstack volume create pure2 --size 10 --type pure
  openstack server add volume T1 pure2
  openstack server remove volume T1 pure2
  openstack server add volume T1 pure2

A patch has been proposed to fix the support [1].

Since we have workaround when 'find_multipaths' is set to 'no'. The
question is: do we want to fix it?

If not, I suggest to document it, that this feature from multipathd
should be disabled. Probably a side-note in the config option
'volume_use_multipath' can help. We could also add a log warning in
os-brick when we detect the issue.


Thanks,
s.

[0] https://bugs.launchpad.net/charm-nova-compute/+bug/1815844
[1] https://review.openstack.org/#/c/638639/
[2] https://docs.openstack.org/nova/rocky/configuration/config.html#libvirt.volume_use_multipath