On Tue, 2009-10-13 at 10:48 -0600, Phil Meyer wrote:
> Yes, multipath -l may not show anything. multipath -v3 should always
multipath -l and multipath -ll will always produce output when there is
an active multipath device on the system (as is the case here) but
that's not what the OP was asking about.
> show similar to the output above, and what you see is that it found two
> paths to the same device, which is good. It is also going to round
> robin reads and writes, which is also good.
That's not correct - the output shows two path groups and the device is
using group_by_prio path grouping policy:
mpath0: pgpolicy = group_by_prio (controller setting)
[...]
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]
So the I/O will only flow over one of these path groups until there is a
failure and we switch to the other path group. I think the newer MSAs
(which this is) do support ALUA which would allow you to distribute the
I/O with some penalty on the non-preferred paths but the default
multipath configuration for this model of MSA will not do this.
> You may want to customize things a bit to make it easier to remember, or
> in case you add another unit or device.
>
> I would suggest adding at least these to /etc/multipath.conf:
>
> multipaths {
> multipath {
> uuid 3600c0ff000d7ba4f4575b24a01000000
> failback immediate
> rr_min_io 1000
> alias san1
> }
The OP was already using the "user_friendly_names" feature. Although
adding explicit aliases is useful in some situations many users prefer
to just use the automatically assigned mpathN names.
> devices {
> device {
> vendor "HP"
> product "MSA2"
> features "1 queue_if_no_path"
> path_checker tur
> }
> }
Why would you override the compiled-in settings for this storage
controller with this? There are two different generations of MSA2*
firmware out there which need different handling - the compiled in
defaults are careful to select the appropriate settings by matching
against the exact product string ("MSA2[02]12fc|MSA2012i" vs.
"MSA2012sa|MSA23(12|24)(fc|i|sa)").
Regards,
Bryn.
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