Attempting to extend a RHEV Storage Domain fails with "Failed to connect Host <UNKNOWN> to device."

Issue

• LUN addition fails with the following error reported in the Events pane in the RHEV-M GUI;

Failed to connect Host <UNKNOWN> to device.

• All the virtual machines on the hypervisor became unresponsive, although the hypervisor itself stayed Up. None of the VM's could be reset, powered off, shutdown, etc.

• An attempt to extend a Storage Domain failed with an ERROR_CANNOT_EXTEND_CONNECTION_FAILED error reported in the var/log/ovirt-engine/engine.log file;

2013-07-05 00:00:51,510 ERROR [org.ovirt.engine.core.bll.storage.ConnectAllHostsToLunCommand] (http-/0.0.0.0:8443-6) [422c5cb6] Transaction rolled-back for command: org.ovirt.engine.core.bll.storage.ConnectAllHostsToLunCommand.
2013-07-05 00:00:51,540 WARN  [org.ovirt.engine.core.bll.storage.ExtendSANStorageDomainCommand] (http-/0.0.0.0:8443-6) [422c5cb6] CanDoAction of action ExtendSANStorageDomain failed. Reasons:VAR__TYPE__STORAGE__DOMAIN,VAR__ACTION__EXTEND,ERROR_CANNOT_EXTEND_CONNECTION_FAILED,$lun