Redundant FCA's using bandwidth of both FCA's simultanously?

[JIm Moser]

I'm trying to increase the Fiber Channel path from my 9000 N-class server to a 3rd party SAN (XioTech). My assumption is that if I install a second FCA and assign both HAB's to the same cluster on the SAN side then HP-UX (11.00) will automaticly utilize both paths, thereby doubling my trunk to the SAN as giving me a level of redundancy in the event that one FCA fails. Am I correct? Would this setup require any configuration on the server/OS side? Has anyone tried this and succeeded/failed?

[JIm Moser]

BTW, I am using Tachyon card. (HP A5158A)

[Glen Hyatt]

Jim,

Adding a second FCA to a system to increase performance & redundancy can be done easily, but is done at the PV level. The inbuilt alternate pathing within LVM can do this in a fashion - it's not load balancing, rather load splitting (ie: Not dynamic).

Say you can see same PV at c2t0d0 and c4t0d0, you can do a vgextend with both device names to use alternate pathing.
eg:
vgextend vg02 /dev/dsk/c2t0d0 /dev/dsk/c4t0d0

The important thing to note is that the FIRST path (c2t0d0) will used for all I/O operations unless that path is down. The way you can load balance over 2 FCA's is by alternating the device name pairs when doing the vgextend
eg:
vgextend vg02 /dev/dsk/c2t0d0 /dev/dsk/c4t0d0
vgextend vg02 /dev/dsk/c4t1d0 /dev/dsk/c2t1d0
vgextend vg02 /dev/dsk/c2t2d0 /dev/dsk/c4t2d0

If you have an existing vg, you can use vgexport and vgimport to achieve the same result.
say...
vgexport -m /tmp/mapfile vg02
mkdir vg02
mknod /dev/vg02/group c 64 0x020000
vgimport -m /tmp/mapfile vg02 c2t0d0 c4t0d0 c4t1d0 c2t1d0 c2t2d0 c4t2d0......

OR
say the disks under c4t?d? are the new paths
use vgextend to add all the c4t?d?'s
use vgreduce every second c2t?d? to make the c4 a primary
then vgextend the c2t?d?'s to add them back, now as the secondary path.

vgdisplay -v will show you which path is being used as the primary. (Always the first entry)

Hope this helps.

[Bill McNAMARA_1]

The OS will not do it automatically.
There is no load balancing as such in HPUX.
You must configure it with LVM volume group create command.

The device file is HW path specific. It doesn't stray.

Later,
Bill