How NPIV can save on fibre cabling for SAN

What is NPIV

NPIV, which stands for N-Port ID Virtualisation is a fibre channel facility allowing multiple N-Port IDs to share a singale physic N-Port. Hence this allows multiple fibre channel to occupy a single physical port, easing hardware requirements in the SAN design.

It is noted that NPIV is an extension to a standard already defined in the fibre channel protocols that allow one to get past single initiator/single target design limitations.

In order to take advantage of this, both the HBA card (from the host and SAN array) and the switch must support NPIV to generate and publish an additional WWPN in a virtual fashion.

Why is it good

Traditionally, we provide at least 2 fibre link for each host, 1 link on 1 controller which is connected to 1 SAN switch in the production environment. With 4 LPARs in the p7 server requiring SAN connection, potentially, we need at least 8 fibre links with 8 SAN ports allocation. Additional links and SAN ports are needed to connect to the SAN arrays.

With the NPIV protocol, we can use just 2 fibre links to connect between the SAN switch and the p7 server. This is a savings of 75%!

Why it may be bad

In the event that there are lots of host sharing the same fibre link, the nightmare of link failure will be catastrophic. It may be mitigated by having 2 HBA controllers with 2 links each, and distributed connection to 2 different SAN switches.