On Wed, 2005-05-25 at 11:18 -0400, Luben Tuikov wrote: > MC/S in iSCSI can be seen as a "wide port" in SAS. > > That is, commands are ordered, nexus is the same, going to the same port, > etc, etc, etc. MC/S, has nothing to do with multipathing, which sits above > the nexus level. With MC/S the nexus is the same. When I use the term "multi-pathing" I mean multiple virtual paths may be traversed to get a command from an application to a target device. Under that definition, dm-multipath, MC/S and even network bonding are all examples of multi-pathing. The visibility of the coding is what I have an issue with. bonding could be inherited invisibly from the network but MC/S has to be explicitly coded in the software initiator whereas dm-multipath is done above the driver: one code base for all multi-path implementations. > MC/S is a good thing. a) It's optional, so you can't rely on it. b) it requires explicit coding in the driver which is a big negative since you can't leverage our existing multi-path code (i.e. more bug prone) c) The feature set it provides to Linux is identical to the feature set that dm-multipath provides. It's pointless to add support for an optional feature that provides no additional benefit (and its detrimental when the only addition is a potential negative impact to the code quality). James - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
