Migrating from arbitrated loop to Switched Fabric - A5158A

[Thomas Yake]

We will soon be migrating from several EMCs with arbitrary loop connections to a single EMC 8730.

All of our HP N&L servers running HP-UX 11.0 have the PHKL_18543 patch. Three of them have PHKL_21381 and driver A5158A 11.00.05. The rest of them will get the revised A5158A 11.00.06 driver and PHKL_23939.

I am relatively new to the topic of Storage Area Networks and was curious if there is a process for migrating from the loops to the switched modes? Do you need to update a file and restart a daemon so the driver and card know the environment has changed? If anyone can shed some light on this I would really appreciate it.

[Michael Tully · Accepted solution]

Hi Thomas,

There are a number of things to plan for with
this type of change.

There is no config file that needs changing.
The HBA cards (F/C cards) are smart enough to
know that the communication has changed but
they need to be told. You will need to initialise
at least one 'ioscan -fn' after the change
from loop to fabric perhaps more. You may also
see a change in the hardware addressing. The
device files of the disks may not change but they
might. This may depend if your are using a switch
or not. You may also need to reboot each of your
HP-UX servers.

Are going through a switch to access this EMC
unit or direct connect from your HBAs?

Some suggestions I have prior to doing anything.
Take a good backup of the entire system. This
includes having an up to date make_recovery tape.
Do an 'export' for each of your volume groups
of your LVM. This can be done by running this
in a preview mode. It will make the necessary
'mapfiles' but not remove any LVM information
from the /etc/lvmtab file.

# vgexport -m yourvg.mapfile -s -p -v /dev/yourvg

If you have a Tape Library unit with F/C switch the
devices also may change. If this occurs you need to
redo your robot device file.

Good Luck

[Thomas Yake]

Thanks for the info!

[Mark van Hassel]

Hi Thomas,

We moved to switched recently. You should check out this URL:
http://techsolutions.hp.com/fc/fabric.htm

Be aware that the PDC requires a certain level as well.
After moving to FC switched the HW paths to your LUNs will be different (because of the different protocol) and therefor you will need to export and import your volume groups with the new device files. ( so you must exactly know what the EMC target/lun addresses of your LUNs are, so you can compare the t/l address of the new HW path with the old one !)
The move to swicthed is best done when the systems are down. We did a few online, but the fibre channel driver starts complaining about nissing loopids etc. It is possible to to get rid of this by a sequence of fcmsutil command, but this is quiet a hassle.
Take a backup beforehand in case things turn out not as expected.