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VA7400 - Accesing the right controller?


VA7400 - Accesing the right controller?


How can I check if I am using the right controller when I access a LUN?

Nguyen Anh Tien
Honored Contributor

Re: VA7400 - Accesing the right controller?

Assume LUN 4 is part of Redundancy Group 2 under Controller 2. An HP-UX
host has two device files that have two separate paths to LUN 4: The primary
device file that addresses Controller 2, and the secondary device file that
addresses Controller 1. The performance path uses the primary device file,
because Controller 2 owns LUN 2. The non-performance path uses the
secondary device file. If the secondary device file is used, data flows through
Controller 1, across the N-way bus to Controller 2, and then to LUN 2 and its
associated disk drives.
HP is simple

Re: VA7400 - Accesing the right controller?

Thanks for the doc, very interesting. Anyway I was asking if anyone has developed a script to check if his system is accessing a LUN using the right controller. I have tried it but it´s not trivial.
Acclaimed Contributor

Re: VA7400 - Accesing the right controller?

The "right" controller is the one that owns the LUN. This should be the primary link to the PV. The first controller will own all LUNs residing in RG1, the second all in RG2.

A very simple way is to inspect the cables from the array to the switch. Note the switch port.
You will find the port in your ioscan, e.g.

disk 3 0/2/1/0/4/ sdisk CLAIMED DEVICE HP

The "29" is the port value, but this depends on your switch model. In case of a B-series 2x00 model this is port 13.

The same result you can get if you compare the WWN of the VA controller (getting from armdsp) and the connected WWN in driver information (fcmsutil).

All is depending on your SAN topology.

Hope this helps!

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