iscsi multipath priority

[benoitc]

I am unsure why but by when setting multipath in failover mode it always take the second interface which is the backup in priority:

root@pve1:~# multipath -ll
mpatha (36e843b6ad25d4d5ddf7dd4af2daf13dd) dm-2 QNAP,iSCSI Storage
size=3.8T features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=50 status=active
| `- 12:0:0:0 sdd     8:48  active ready running
`-+- policy='round-robin 0' prio=50 status=enabled
  `- 13:0:0:0 sdc     8:32  active ready running

root@pve1:~# more /etc/multipath.conf
blacklist {
        wwid .*
}

blacklist_exceptions {
        wwid "36e843b6ad25d4d5eef7dd4af2daf13dd"
}


defaults {
        user_friendly_names    yes
        polling_interval        2
        path_selector           "round-robin 0"
        ##path_grouping_policy    multibus
        #uid_attribute           ID_SERIAL
        rr_min_io              100
        failback                immediate
        no_path_retry           queue
}

How to make it choose sdc instead?

 

[apoc]

If your storage uses alua then it can signal the host which path to use.
Is your qnap a dual-controller system?

 

[benoitc]

it has 2 nics at least but i don't see where i can put the priority

 

[apoc]

If it only has two nics and no dual-controller then there os no controller preference that could bother you here.
From an ALUA-perspective both ports are equally handled as they belong to the same controller.
What are the reasons you want to pin the traffic to a certain path?
The whole idea of round-robin is to balance traffic between paths and in the end it will hit the very same controller anyways?!

 

[benoitc]

well i wanted to do dome failover since the 2 links are not on the same switch. also in peiority use the 10G link, the other one is a 5G link.

 

[apoc]

in which case you will likely need move away from alua and just do a "blank" active / standby policy

 

[benoitc]

if i force the order of the sesdion it mostly work. though i can simply load balance indeed.