On Fri, Apr 06, 2012 at 11:29:47PM -0700, Ray Van Dolson wrote: > 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 It seems like what I'm after is "prio_callout". However, it doesn't seem to be documented in the man pages (though it is in one of the sample configurations). I tried setting path_grouping_policy to group_by_prio and then defined prio_callout to point to a bash script on my system that echo's "2". This doesn't seem to actually get called though. Actually, after doing a bit more reading it sounds like prio_callout was replaced by "prio" in RHEL6's version of the tool. "prio" doesn't appear to have an option to call a custom script. :( Ray -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
