topic Re: VA7400 - Accesing the right controller? in Disk Enclosures

VA7400 - Accesing the right controller?

Mario_88 — Wed, 03 May 2006 13:21:35 GMT

Hello:

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

Regards.

Re: VA7400 - Accesing the right controller?

Nguyen Anh Tien — Thu, 04 May 2006 01:52:59 GMT

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.
PLS REVIEW ATTACED FILE FOR MORE DETAILED

Re: VA7400 - Accesing the right controller?

Mario_88 — Thu, 04 May 2006 09:59:14 GMT

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 itÂ´s not trivial.

Re: VA7400 - Accesing the right controller?

Torsten. — Thu, 04 May 2006 14:22:44 GMT

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 0/2/1/0/4/0.1.29.0.0.0.0 sdisk CLAIMED DEVICE HP
A6188A

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.