Re: generating a Linux WWN?

Jeff Garzik
2007-09-27T14:19:26Z

James Smart wrote:
> Uh, although this may work very well for small constrained configs, as one
> who debugs larger environments (and things always grow or get connected in
> ways you don't expect), depending on a random number for uniqueness makes
> me very unsettled. Debugging that small-percentage potential, when/if it
> does occur can be an absolute nightmare with all kinds of weird behavior.
> Rarely will you solve it from the context of a single server. There are
> lots of ways to cheat, but I believe they all have to be based on some
> small part that is guaranteed to be unique (like the IEEE id's).

That's the ideal world, sure :)

But the reality is, just like with ethernet MAC addresses, you don't
always have one when you "supposed to" have one.

There are obvious limitations and problems arising from a generated WWN
-- particularly for an HBA, where serial numbers and other unique
identifiers are scarce. But that doesn't wish the missing-WWN problem
away. Decades of networking experience have taught us a few things :)

As an aside, we also need a way to override the HBA's WWN, just like we
do with ethernet MAC address.

Jeff