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Re: [dm-devel] 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/focus=4435

Regards
--
Tore Anderson


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