Ben, I'd like to summarize all the issues I raised recently through my employers support channel on the multipath subsystem. And see if something can be done about it, at least in the upstream concerned codebases. 1/ multipathd private namespace pins lvm2 logical volumes maps mounted at daemon startup, thus making "vgchange -ay" fail, even after umounting the visible mount. In my context, it also means I can't stop a clustered service build on this vg to start it on another node. This problem does not affect upstream which does not create a private namespace. 2/ can't map a rw multipath over read-only paths. Quick workaround to create ro multipath, but ro->rw promotion is not automatic when paths become writable. I keep thinking we should allow rw multipath over ro paths. The ro->rw event might also work, but what will trigger the kernel rw status change in the first place ? To my knowledge, only a manual scsi device rescan can force this status update ... which accounts for a less user-friendly solution than the former. 3/ Can't use scsi-3 persistent reservations on clariion multipathed luns : paths reserved on node A, writes submitted on node B should be errored immediately to ensure data integrity. Instead, writes get buffered in the "queue_if_no_path" logic, and finally corrupt the data when reservation get cleared. In my context, reservation is the prefered io fencing method for clusters. The kernel knows the write io submitted on a path is refused due to a reservation conflict, but this status is not propagated to multipath for it to react by not queuing this io as it should. Regards, cvaroqui -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
