[ovirt-users] Error while extending a cinder/ceph disk

Hi, when trying to extend a ceph disk in ovirt 4 (Virtual Machines => Edit Virtual Machine => Instance images => Edit => Extend size by) I get the following error: Error while executing action: interface is required In engine.log I see the following errors as well: 2016-07-21 15:14:55,266 ERROR [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (default task-35) [] Correlation ID: 47ce3344, Call Stack: null, Custom Event ID: -1, Message: Failed to update VM test01 disk test01_Disk1 (User: admin@internal-authz). 2016-07-21 15:14:56,091 ERROR [org.ovirt.engine.core.bll.storage.disk.cinder.ExtendCinderDiskCommandCallback] (DefaultQuartzScheduler8) [2819eb7c] Failed extending disk. ID: a5dd90b1-3a76-4e38-af8c-e829b3b86a40 2016-07-21 15:14:56,124 ERROR [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (DefaultQuartzScheduler8) [2819eb7c] Correlation ID: 2819eb7c, Call Stack: null, Custom Event ID: -1, Message: Failed to extend size of the disk 'test01_Disk1' to 20 GB, User: admin@internal-authz. 2016-07-21 15:14:56,209 ERROR [org.ovirt.engine.core.bll.storage.disk.cinder.ExtendCinderDiskCommand] (DefaultQuartzScheduler8) [2819eb7c] Ending command 'org.ovirt.engine.core.bll.storage.disk.cinder.ExtendCinderDiskCommand' with failure. After this, the cinder image is flagged as illegal and I can just delete it. Extending the image on the cinder side is possible, and the command "cinder extend <id>" works, but then the new size is not properly reported back in ovirt. Any clue? Thanks, Alessandro