Multipath command output - Help with understanding output

[Bryn M. Reeves]

On Tue, 2009-10-13 at 17:17 +0100, Dan Track wrote:
> I've configured multipath but I'm confused with the following. When I
> run "multipath -v2" I don't get any output, but if I run "multipath
> -v3" I get lot's of output e.g.:

<snip>

> mpath0: pgfailback = -2 (controller setting)
> mpath0: pgpolicy = group_by_prio (controller setting)
> mpath0: selector = round-robin 0 (controller setting)
> mpath0: features = 0 (internal default)
> mpath0: hwhandler = 0 (controller setting)
> mpath0: rr_weight = 1 (internal default)
> mpath0: minio = 100 (controller setting)
> mpath0: no_path_retry = 18 (controller setting)
> pg_timeout = NONE (internal default)
> mpath0: set ACT_NOTHING (map unchanged)

^^ here's why you're seeing no output from "multipath -v2". At this
verbosity level the command only prints output when it changes
something. Since your mpath0 device was already up and running at this
point there's no changes to make and -v2 will be silent.

If there's nothing using the device then you can try running "multipath
-F" to flush all multipath devices then re-running "multipath -v2" -
this should re-create the map and print something to the terminal
indicating what it's done.

> 
> multipath -ll
> mpath0 (3600c0ff000d7ba4f4575b24a01000000) dm-0 HP,MSA2012sa
> [size=9.1T][features=1 queue_if_no_path][hwhandler=0][rw]
> \_ round-robin 0 [prio=50][active]
>  \_ 0:0:0:1 sda 8:0   [active][ready]
> \_ round-robin 0 [prio=10][enabled]
>  \_ 1:0:0:2 sdb 8:16  [active][ready]
> 
> Does that mean multipath is working on /dev/sda and /dev/sdb? Is the

Yes.

> lack of output for "multipath -v2" a concern?

No.

Cheers,
Bryn.