Tore I have found the definitions of all CX failover modes. The SAN admin assigned failover mode 3. Will DM support option 3 assuming that I follow EMC's guidance wrt the appropriate settings for the CX in multipath.conf? ... Or should we reassign the failover mode to 1 per your email? It seems to me that the path state status will differ significantly based on the failover modes; specifically 1 or 3. We don't have FLARE 26 so ALUA mode is N/A. The failover definitions are: 1) Passive not ready; a command failure when I/O issued to non-owning SP. 2) quiet trespass on I/O to non-owning SP 3) passive always ready; some commands (TUR) return "passive always ready" status. -----Original Message----- From: dm-devel-bounces@xxxxxxxxxx [mailto:dm-devel-bounces@xxxxxxxxxx] On Behalf Of Tore Anderson Sent: Monday, November 19, 2007 1:51 PM To: device-mapper development Subject: Re: CLARiiON failover modes and DM. * Paul Cote > Is there a specific failover mode that the CX must be set for DM > interoperability? You have (at least) two options. CLARiiON Open mode 1 is the traditional way where all paths to the passive controller is present but will refuse almost all I/O operations. You'll need to be using the "emc" hardware handler for that to work, since a proprietary command needs to be sent to a path to the passive controller in order to trespass the volume there. The other option (which is only available in FLARE 26) is ALUA mode (CLARiiON Open mode 4), where I/O is accepted on both controllers even though only one is the one handling all the I/O. You can use this without a hardware handler (there's one in developement, though), but you'll still want to be prioritising the paths to the preferred controller for optimal performance. This is the mode I would prefer, at least. I wrote a bit more about the ALUA mode a few days ago: http://thread.gmane.org/gmane.linux.kernel.device-mapper.devel/4366/focu s=4435 Regards -- Tore Anderson -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
