On Wed, 2005-05-25 at 14:04 -0400, James Bottomley wrote: > 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). Those are very strong arguments against having MC/S implemented for the software iSCSI initiator. Especially true is (a). Not that many targets offers MC/S, since according to RFC it implies ERL=2. Now, back to open-iscsi initiator business and its mainline acceptance. We are going to met your requirement and will remove multi-connection support before next patch-set submission. As Mike C. mentioned before, it is fairly easy to do since the whole connection management resides in user-space. Though it will exists as a kernel patches on our web site (http://www.open-iscsi.org) for those who wonders. Are there are some other requirements we need to met besides MC/S removal ? Thanks for the good explanation of your point of view! Dima > 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
