Why WWPN of the controller required for SAN boot/ wat is the use of WWN when we use only WWPN?

[narendrakumarg]

Am new to storage...
Why controller WWPN is required for SAN boot? (Through VCM we provide controller WWPN) Can we just present a LUN in EVA and make the LUN bootable without providing controller WWPN? Any way?

I have one more question.

Why are we having WWN for a HBA/EVA when we will use only WWPN of it? If it is not used any where, are we not wasting one WWN number for it?

[Steven Clementi]

"Can we just present a LUN in EVA and make the LUN bootable without providing controller WWPN? Any way?"

No. In order to "find and identify" LUN's available for booting... the server needs to know where to look. (i.e., "Which Storage Array has my bootable LUN?")


"Why are we having WWN for a HBA/EVA when we will use only WWPN of it? If it is not used any where, are we not wasting one WWN number for it?"

I assume that you are referring to the difference between WW "node" name and WW "port" name... ?

A device is a node. It needs an "address"

A port on that device also needs an address since there could be multiple ports available... (I.E. an EVA8000 has 8 ports. The Node Name ends with 0 while the ports end with 8,9,A,B,C,D,E and F)


Steven

[SunnyS]

Well, as per FC spec, each FC port must have a PWWN and a NWWN. Also, as per FC spec, PWWN must be globally unique. However, NWWN need not be unique. So, it is entirely possible that multiple ports on a given controller may have the same NWWN. But they must have different (and globally unique) PWWNs.

[narendrakumarg]

Thanks Sunny and Steven.
@ Sunny: But is there any use of WWN of the node? I have not seen its use any where.

[SunnyS · Accepted solution]

NWWN is useful for SAN management applications. Here is an example of a controller with 4 ports and their NWWNs & PWWNs.

FC port #1 has NWWN-1 and PWWN-1.
FC port #2 has NWWN-1 and PWWN-2.
FC port #3 has NWWN-1 and PWWN-3.
FC port #4 has NWWN-1 and PWWN-4.

As you can see with the same NWWN, it is trivial for SAN management applications/software to figure out that all these 4 FC ports actually belong to the same "node".

This is just one example. There are other uses for it as well.

[narendrakumarg]

Thank you Sunny, can you please share a doc which gives a clear basic understanding of SAN.

Thanks,
Narendra

[Steven Clementi]

I don't think you'll find anything thats "clear and basic"



A SAN is... a Storage Area Network. Just like a LAN is a Local Area Network that interconnects different computers and computer resources (Printers, other networks, the Internet, etc.).. a SAN interconnects various storage related resources to various servers that need access to those devices. Storage devices include Storage Arrays, Tape Libries and/or Silos, iSCSI/FCiP gateways, etc.


You can start here...

The HP SAN Design Guide:
" http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c00403562/c00403562.pdf "

It's not clear and basic, but it does have some explainations of things.


Steven