Re: [linux-lvm] SAN Storage/mirror/lvm

[Cott Lang <cott@internetstaff.com>]

>I setup a similar system on a HDS-9570 but with only one
>card in each machine - 'assuming' that the failover in the
>driver would cope if a controller on the HDS failed (as
>opposed to a QLogic failure)
>
>This worked fine if I disconncected a path in the fabric but
>when we took a controller of line the failover failed.
>
>Since then I have used md multipath which has tested fine

I have a similar issue, two storage processors, two HBAs, and
redundant paths between them.

On the host, I see 4 SCSI devices, two valid, two invalid - I'm 
guessing this is caused because only one storage processor exports
a particular LUN, so half the paths are invalid until a storage
processor fails over.

sdd - SP A Path 1
sde - SP B Path 1
sdf - SP A Path 2
sdg - SP B Path 2

I have a LUN currently on SP B, so I can use md multipath configured 
with /dev/sde and /dev/sdg, and that seems to work.

However, two things:

1) How do I set this up to handle a failover to SP A?
2) Multipath only seems to work in failover mode, is there a way to
load balance across the two paths?

Anyone have any hints?  :)