[linux-lvm] LVM Multi Path Support

[Markus Baertschi]

I'd like to relate my experiences with multipath support and LVM.
We have an installation with several DB servers connected with
fiber to a SAN unit. All connections are doubled.
- Two fiber cards (Qlogic)
- Two switches
- SAN unit with dual controller (IBM FAStT 700)
We have tested the failover facilities provided by the qla2300-fo driver (pulled fibers) and they work. Each disk shows up once and the driver takes care of the failover facility.

However, we had one very nasty experience last summer. After rebooting (for an unrelated reason) the machines didn't came back up. The vgscan during boot dumped core. The reson was that somebody reconfigured the SAN unit and the controllers now had different WWNames. As a result the disks showed up twice and our (out of date) LVM could not handle it. Pulling one fiber/path temporarily fixed our problem. Upgrading to the latest LVM code fixed the coredump also. But we have not tested if failover would work that way.

Markus
-- 
  Markus Baertschi             Phone: ++41 (21) 807 1677
  Bas du Rossé 14b             Fax  : ++41 (21) 807 1678
  CH-1163, Etoy                Email: markus at markus.org
  Switzerland                  Homepage: www.markus.org