Hello again. Just in case someone is pulling this from the list archives, here's the sum-up for the record. This is my procedure for testing SCSI-2 reservations and preempting them, thus simulating a MSCS failover procedure from a Linux open-iSCSI host. With slightly different results for STGT and IET. With tgtd 0.9.8: Node A: # sg_raw /dev/sdc 16 00 00 00 00 00 SCSI Status: Good Sense Information: sense buffer empty Node B, immediately afterwards: # sg_raw /dev/sdc 16 00 00 00 00 00 SCSI Status: Reservation Conflict Sense Information: sense buffer empty Good, now preempting the reservation with a device reset on node B: # sg_reset -d /dev/sdc sg_reset: starting device reset sg_reset: completed device reset (Alternatively, a host reset on node B works too) # sg_reset -h /dev/sdc sg_reset: starting host reset sg_reset: completed host reset Afterwards, on node B: # sg_raw /dev/sdc 16 00 00 00 00 00 SCSI Status: Good Sense Information: sense buffer empty Whereas, on node B this just hangs: # sg_reset -b /dev/sdc sg_reset: starting bus reset Thus, preempting the reservation via a host or device reset works, whereas via a bus reset it appears not to. It appears that MSCS (at least in the Windows 2003 version) uses bus resets to preempt reservations on quorum devices for cluster node failover. It says in a support article (http://support.microsoft.com/?scid=kb%3Ben-us%3B309186&x=12&y=9) that with storport drivers MSCS uses a device reset instead of a bus reset, which works fine with tgt. I would assume that this does not apply to using the MS iSCSI initiator -- Ross, maybe you can correct me if I'm wrong here? Conversely, here's the same procedure with IET 0.4.17: Node A: # sg_raw /dev/sdc 16 00 00 00 00 00 SCSI Status: Good Sense Information: sense buffer empty Node B, immediately afterwards: # sg_raw /dev/sdc 16 00 00 00 00 00 SCSI Status: Reservation Conflict Sense Information: sense buffer empty Device reset on node B: # sg_reset -d /dev/sdc sg_reset: starting device reset sg_reset: completed device reset (Alternatively, a host reset on node B works too) # sg_reset -h /dev/sdc sg_reset: starting host reset sg_reset: completed host reset And here, a bus reset works as well: # sg_reset -b /dev/sdc sg_reset: starting bus reset sg_reset: completed bus reset Afterwards, on node B: # sg_raw /dev/sdc 16 00 00 00 00 00 SCSI Status: Good Sense Information: sense buffer empty Hope this is helpful. Cheers, Florian
Attachment:
signature.asc
Description: OpenPGP digital signature
