On Thu, Apr 25 2013 at 11:27am -0400, Bryn M. Reeves <bmr@xxxxxxxxxx> wrote: > On 04/25/2013 03:50 PM, Mikulas Patocka wrote: > >On Thu, 25 Apr 2013, Mike Snitzer wrote: > >>The handler that is automatically attached _should_ be the correct > >>handler. We now have the .match() hook for scsi_dh and it has made for > >>reliable scsi_dh attachment of the correct handler. > > > >The EMC devices work with both ALUA and EMC handlers - so there is no one > >"correct" handler, the correct handler is the one that the user specified > >in multipath configuration. > > I think it's more absolute than that; if a Clariion array is in > failover mode 4 (ALUA) then it's incorrect to use scsi_dh_emc and > vice-versa. > > The user can configure this in multipath.conf but it does not make > it correct. The correct handler is the one that matches the > configured failover mode of the array. > > The ALUA handler scsi_device_tgps() in its match function but since > the scsi_dh_emc match function only looks at the vendor/product it's > impossible for it to make the correct decision. > > The array can tell us what mode it's running in - teaching > scsi_dh_emc to do this would seem to be an improvement. clariion_match does more than check the vendor and product; if tpgs is set (ALUA mode) it returns false. So yes, while there is room for improvement in clariion_match the current code should work just fine with reasoning between emc and alua. -- To unsubscribe from this list: 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
