What is the use of LUN WWN?

[narendrakumarg]

Where is LUN WWN used? We usually use LUN ID (1-255)while presenting the LUN, where we can give same LUN ID to many LUNs and present it to the host. How does the mapping happen when many LUNs can have same LUN ID? Please describe.

Thanks,
Narendra

[Steven Clementi]

LUN = Logical Unit Number (as it pertains to storage)

In some storage arrays...

the Lun Id is a presentation setting per server, not per logical disk. For instance:

On an EVA, I have vDisk 1 and vDisk 2. Server 1 needs access to both luns and server 2 needs access to only lun 2.

I can present vDisk 1 to Server 1, using LUN Id 1 and vDisk 2 using LUN Id 2.

For Server 2, I can present vDisk 2 using LUN Id 1.

The LUN Id only allows the OS of the server to distunguish between other LUNs.

The OS distinguishes each LUN using more than just the LUN Id. Each vDisk (LUN) would have a full address including the port and bus it is on. It could also use the unique identifier of the LUN which the Storage Array assignes to it upon creation... the LUN WWN (or what looks similar to a WWN).


Steven

[narendrakumarg]

Thank You Steven,

But is there any document or any where is it mentioned that how this mapping happens between LUN WWN and Server (OS)?

Can you please give me a document which describes how the communication happens between LUN and the Server (LUN->Controller->HBA->OS)?

Thank u very very much!
Narendra