Re: generating a Linux WWN?

Luben Tuikov
2007-10-08T18:34:45Z

--- Jeff Garzik <jeff@garzik.org> wrote:

> James Bottomley wrote:
> > My problem with auto generated is that it's provably impossible to
> > generate globally unique numbers for WWNs without some internal source
> > of uniqueness (I know sparcs have this in their serial number, but most
> > PCs unfortunately don't).
> >
> > I know the auto generated number can be statistically reasonably unique,
> > but sysadmins are lazy people. If they run into this problem, they'll
> > take the knob with the on/off switch rather than the think about the
> > problem and specify the full WWN; and then, being busy people, they'll
> > forget about it as "problem solved". When they do this, statistically
> > (and probably years later) there will be a cluster reboot where the
> > entire SAN simply collapses and no-one knows why ... the poor SAN
> > administrator will likely spend weeks working out the problem is.
>
> Why, if we give lazy administrators root access, that's all they'll use,
> and they will just think "problem solved" until a serious security issue
> arises that takes down the cluster.
>
> See how silly and un-Linux that logic is? In Linux, the admin has the
> power to make stupid decisions -- or to make informed decisions that
> disagree your rigid "an admin should never do that" line of thought.
> It's their hardware.
>
> You're also using the 1% case of a 1% case of a 1% case to argue against
> a feature that is useful in making things Just Work(tm).

What he's arguing about is the _capability_ for a node in a SAN
to *(auto)generate* WWN and assign it to itself (at every
reboot, etc). This is considered a _rogue_ node and *no* SAN
architect or admin will tolerate such a node.

The problem here is NOT the _capability_ to assign a WWN.
Admin does have the capability to assign (if missing) and/or
override (if present) a WWN currently with aic94xx driver.
This is fine.

The problem is "(auto)generate". Think of SANs.

Luben