Subject: Re: System unique identifier.....
To: Matthew Jacob <>
From: Eduardo E. Horvath <>
List: tech-kern
Date: 06/25/1999 08:33:26
On Thu, 24 Jun 1999, Matthew Jacob wrote:

> Specifically in this case a Node WWN for fibre channel fabrics that does
> not depend upon an assigned WWN in any particular Fibre Channel card
> (multipathing might make it desirable to have a synthetic Node WWN that
> can also be passed to partner systems in  a failover configuration).


We've been hashing this issue out quite a bit.  Since a Fibre Channel card
is by definition a fibre channel controller, each card should have a
unique WWN that is used for the node WWN.  If you swap a controller, the
node WWN should change.

The concept is that for SCSI disks and RAID boxen at least, the unique
identifier is the LUN WWN, which is the unique label for the data
contained on that LUN.  The LUN WWN is 128 bits wide is generated from a
combination of the controller's node WWN and a timestamp, and is lost when
the LUN is destroyed.

If you're not dealing with SCSI disks, well, I don't know if the standards
guys have considered that sort of situation yet.  

Eduardo Horvath
	"I need to find a pithy new quote." -- me