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 Storage Virtualize PBHA and AIX multipathing

Brad McArdle's profile image
Brad McArdle posted Mon January 13, 2025 12:28 PM

Hi,

 

We traditionally configure AIX LPARs for fully redundant pathing through both SAN fabrics and both VIO servers. This results in 8 paths per volume, like this:

As 8 paths per volume is the maximum supported for AIX hosts on Storage Virtualize, that works out well:

If we were to implement Policy-Based High Availability (PBHA), however, the number of paths would double, to 16 paths per volume. As this is beyond the supported limit of 8 paths per volume, what is IBM’s recommendation for pathing configuration when using AIX/VIO/PBHA together? What do we “cut out” to get that down to 8 paths per volume, if that is required?

 

Thank you in advance for any insight you can provide.

Bradley McArdle

Sr. Systems Engineer

ATS Group

brad.mcardle@theatsgroup.com

Zaki Jääskeläinen's profile image
Zaki Jääskeläinen posted Tue January 14, 2025 02:03 AM

I would drop the yellow and green paths. You still end up with each AIX vFC connecting to both controllers and one fabric per vFC and one VIO per vFC.

Next LPAR uses the yellow and green paths.

Hans Populaire's profile image
Hans Populaire posted Tue January 14, 2025 02:28 AM

In our environment, we zone each fcs only to 1 node of the iogroup and therefore we end up with 4 paths per LUN (2 active and 2 standby) :

SANA      fcs1(VIO1)          node1 port1

SANA      fcs3(VIO2)          node2 port1

SANB      fcs0(VIO1)          node2 port2

SANB       fcs2(VIO2)         node1 port2

 

This gives you all the required redundancy and failure of fabric, VIOS or node always results in a situation that all other resources are still used.

So drawing is ok, except the split at the right end where each path goes to both nodes.

Also need to add here that we then use port 1 and 2 on each node for 1 LPAR, another LPAR will then use 3 and 4.

That way we distribute the load on the ports across multiple LPAR's.

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