[TriLUG] Mutipathing under 2.6.x - udev/multipath/hotplug

[Greg Foster]

Hi Folks,

Please excuse in advance if you've covered this already.  I'm setting
up some fibre channel storage for MythTV, and want to achieve either
'active/active' or active/passive' between the drives and the host.

Since FC-AL drives are dual-ported, they present themselves twice on
the Fabric (using a Brocade 2800 switch).  With (2) hbas, I see 4
devices per target.  It's my understanding that between udev
(persistent naming) and device-mapper (along with multipath tools) I
should be able to transparently have a path go away and continue
working (much like Veritas' DMP offering, or EMC's PowerPath.

I've got 2.6.12-rc2 installed, and multipath seems to fire up.  Anyone
have any experience with what device names to actually use (or do I
need to create naming rules in UDEV first?) when wanting to have
failover happen in the background ?

As a side note, I have tried the 'mdadm' method of creating a
multipath device, and then using a set of those devices to create a
raidset.  Strictly passive active though, although I suppose I could
reference the other half of the devices with the alternate path first.

For reference, I'm using 8.0.27 of the 2.6 driver (no patches applied,
not required I believe).


Thanks in advance,
Greg.