Finding VA7400 optimum data paths

[Timothy Czarnik]

Hey all,

I have a VA7400 plus 3-2405 expansion cabinets (total of 60 disks). The VA7400 has 2 controllers. Our N-class server has 2 fibre cards. All of these connections are run through a fibre switch so that when I assign a LUN to the N server I can see that space down 4 different paths (and it shows up as 4 different disks).

Now, I'm not sure if I'm just missing something really simple or what, but how I do determine that the disk I assign as the primary disk in the volume group is the best path to the data? How am I able to tell, on the Unix side, which disk to use as the primary and which disks to assign as the pvlinks disk?

Also, can someone point me to some things I should be watching for as far as performance red flags and things of the such. (No, I haven't yet searched the forums for this info, but since I was here anyway...)

Thanks in advance!

Tim

[Uwe Zessin]

Tim,
each VA7400 controller should be identifiable through it's port WWNs, but I am not a HP-UX administrator, so I am afraid I can't help here.

The VA7400 provides two redundancy groups into which the LUNs are created. RG1 is maintained by controller-1, RG2 by controller-2. You can access any LUN in RG1 through controller-2, too and vice versa, but each controller will pass on the request to the other one over an internal bus.

So it is best to access the LUNs directly through the controller that maintains the RG in which the LUN resides.

[Timothy Czarnik]

Uwe,

I am familiar with the redundancy groups and WWN numbers. The goal is to make sure that any LUN created in RG1 has it's primary path being to controller 1 on the VA7400. That's where I fall down.

Here's my example:

I create a LUN on the VA7400. Because the VA7400 has 2 connections to the SAN, and my N server has 2 connections to the SAN, I see that disk down 4 different paths and it shows up as 4 different disks in my ioscan. I don't know how to determine which of those 4 disks to use to ensure that I have the fastest path as primary path (i.e. using the controller 1 for RG1 and controller 2 for RG2).

[David Bell_1 · Accepted solution]

Tim,

See if the attached document helps. It will show you how to identify the locations of what you see in ioscan.

HTH,

Dave

[Uwe Zessin]

Yes, right! The FCID is part of the hardware path. It is too bad that I don't have a NVbrain :-(

You can find out the hardware address and the WWPN of the fibre channel adapter with:
# fcmsutil /dev/td0

I assume you have a Brocade switch. In that case you can verify the connectivity with:
> switchShow

Different switches, firmware or configuration settings can cause a different FCID on a port (sometimes the area is equal to the port number, sometimes it is port number+16 and other variants are possible). In that case I would check the name server as this matches the WWPN with the assign FCID.
> nsShow

[Timothy Czarnik]

What would I do without the forums? :)

Thanks for your help!