>We want to use both FC ports of the 3590 drives (connected via a FC
>fabric)in parallel for automatic path fail over. Is this supported by AIX
>and how could this be implemented in AIX. At the moment I see for the same
>drive two definitions in AIX. They are both available but they doesn't
work
>in TSM (drives are first polled by TSM and set to unavailable later on).

>Do you have a recommendation for defining both pathes to AIX in parallel
for
>dynamic path fail over?


>Thank you in advance
>Uwe

If you look at the tape drive charataristics in AIX, there is an option
called "Enable alternate pathing support".
I suppose this has to be involved in getting alternat paths to work.

I have not yet found anywhere in the AIX documentation where this is
documented, but I have not looked everywhere
yet :-)

We have two FC adapters in the host and therefore have two definitions for
each of our four physical tapedrives.
In our case rmt0=rmt3, rmt1=rmt2, rmt4=rmt6 and rmt5=rmt7.
If we had been using both FC connections on the drives as well, I suppose
we would have had four instances of
each drive.

You can check the WWPN of the drive to verify which is what.

I have tried to enable alternate pathing support and this causes the
connection name of 30-58-01 to change to
30-58-01-PRI for the first instance of the drive and 20-58-01 to
20-58-01-ALT for the second instance of the drive.

I have had no problems with the drives being switched offline and TSM did
function OK with the drives.
However, I saw a tendency to have I/O concentrated on one of the FC
adapters while the other adapter was only
slightly used, so I turned off the alternate pathing support again and
defined the drives to TSM with two on the
one FC adapter and two on the other adapter. This keeps the load balanced.

Perhaps we need a tape version of the disk DPO (Data Path Optimizer)
software which collects all paths to a disk
under one name and does a good job of balancing I/O or perhaps we only need
to read the documentation if
we can find it.

If anybody knows where the "Alternate pathing support" may be documented, I
would be happy to hear about it.

Regards

Peter








pathing support