I am setting up multipathing on RHEL6 via iSCSI to an IBM XIV. My iSCSI target looks like this: 172.16.10.1:3260,1793 iqn.2005-10.com.xivstorage:003974 172.16.8.22:3260,2048 iqn.2005-10.com.xivstorage:003974 172.16.10.22:3260,2049 iqn.2005-10.com.xivstorage:003974 172.16.8.23:3260,2304 iqn.2005-10.com.xivstorage:003974 172.16.10.23:3260,2305 iqn.2005-10.com.xivstorage:003974 172.16.8.1:3260,1792 iqn.2005-10.com.xivstorage:003974 (This is one LUN). Networks are 172.16.10.0/23 and 172.16.8.0/23, so as you can see above there are three target IP's on each subnet. My RHEL6 host has two physical uplinks... one to each subnet. When I configure multipath, by default it creates one big path group with all of the devices above within it and round-robins. mpathb (2001738000f860110) dm-2 IBM,2810XIV size=48G features='1 queue_if_no_path' hwhandler='0' wp=rw `-+- policy='queue-length 0' prio=1 status=active |- 26:0:0:1 sdb 8:16 active ready running |- 25:0:0:1 sdc 8:32 active ready running |- 27:0:0:1 sdd 8:48 active ready running |- 24:0:0:1 sde 8:64 active ready running |- 23:0:0:1 sdf 8:80 active ready running `- 22:0:0:1 sdg 8:96 active ready running This results in less than ideal performance. Ideally I want to only have one path per subnet active at any given time, with the other paths only activating if there's a failure. The only other option I seem to have is to set path_grouping_policy to failover. This creates six separate path groups of which only one is active at a time. I thought perhaps I could do group_by_prio, but am not sure how I can manually set priorities for my underlying physical iSCSI devices, and the default "const" method just gives them all priority 1 so they all end up in the same path group again. It looks like perhaps I could configure path groups as I want manually with dmsetup, but I'm sure there's a better way... As it is I am currently just configuring my iSCSI initiator to log in to only one target per subnet. This gets me the best performance but I lose some (automated) redundancy. Thoughts appreciated. Ray -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
