I have earlier mentioned on my blog that I will publish my study guide for VMware Enterprise Administration Exam, but as I have been preparing for my design exam & killed with projects at work. I really had no time to put it all online. Further, it seems these exams are expiring soon. For that I have decided to only publish the most ignored chapters required for the VMware Enterprise Administration exam & VMware Design Exam. I will start with NPIV. When I was preparing for my exam beside the Exam blueprint NPIV was not covered in any study guide including the DSA materials. As I did not use it much in real life I had got a bit of exposure and note taken while reading the chapter about it in the Fibre Channel SAN Configuration Guide which should be almost of sufficient knowledge for both VMware Enterprise Administration Exam & VMware Design Exam as I assume at least. Below are my note of NPIV.

NPIV enables a single FC HBA port to register several unique WWNs with the fabric, each of which can be assigned to an individual virtual machine. When a virtual machine has a WWN assigned to it, the virtual machine’s configuration file (.vmx) is updated to include a WWN pair (consisting of a World Wide Port Name, WWPN, and a World Wide Node Name, WWNN).

As that virtual machine is powered on, the VMkernel instantiates a virtual port (VPORT) on the physical HBA which is used to access the LUN. The VPORT is a virtual HBA that appears to the FC fabric as a physical HBA, that is, it has its own unique identifier, the WWN pair that was assigned to the virtual machine. Each VPORT is specific to the virtual machine, and the VPORT is destroyed on the host and it no longer appears to the FC fabric when the virtual machine is powered off.

If NPIV is enabled, four WWN pairs (WWPN & WWNN) are specified for each virtual machine at creation time.When a virtual machine using NPIV is powered on, it uses each of these WWN pairs in sequence to try to discover an access path to the storage. The number of VPORTs that are instantiated equals the number of physical HBAs present on the host up to the maximum of four. A VPORT is created on each physical HBA that a physical path is found on. Each physical path is used to determine the virtual path that will be used to access the LUN.Note that HBAs that are not NPIV aware are skipped in this discovery process because VPORTs cannot be instantiated on them

NOTE: If a user has four physical HBAs as paths to the storage, all physical paths must be zoned to the virtual machine by the SAN administrator. This is required to support multipathing even though only one path at a time will be active.

NOTE: If you want to use VMotion for a virtual machine with enabled NPIV, make sure that the RDM file is located on the same datastore where the virtual machine configuration file resides. You cannot perform Storage VMotion, or VMotion between datastores, when NPIV is enabled.

NOTE: You can enable NPIV for a VM while creating it or after turning it off from virtual machine settings. Hint Hint: a virtual machine need to be turned off to enable NPIV.

Requirements & Limitations for Using NPIV:

Before you attempt to implement NPIV by assigning WWNs to your virtual machines, be aware of the following requirements and limitations:

1. NPIV can only be used for virtual machines with RDM disks. Virtual machines with regular virtual disks use the WWNs of the host’s physical HBAs.
2. For this implementation of NPIV, the physical HBAs on an ESX Server host, using their own WWNs, must have access to all LUNs that are to be accessed by virtual machines running on that host.
3. The ESX Server host’s physical HBAs must support NPIV. Currently, the following vendors and types of HBA provide this support: QLogic – any 4GB HBA & Emulex – 4GB HBAs that have NPIV compatible firmware.
4. Only four WWN pairs are generated per virtual machine.
5. When a virtual machine or template with a WWN assigned to it is cloned, the clones do not retain the WWN.
6. The switches used must be NPIV aware.
7. When configuring an NPIV LUN for access at the storage level, make sure that the NPIV LUN number and NPIV target ID match the physical LUN and Target ID.
8. Always use the VI Client to manipulate virtual machines with WWNs.

Please go over the above post twice, as it seems most of us are not exposed to NPIV as much we should & both VMware Enterprise Administration Exam & VMware Design Exam have listed them as items that can appear on the exam. Please post your comment or extras you want to share about NPIV with us in the comment area below.