Re: inventory

[Alan Robertson <alanr@unix.sh>]

Greg Lindahl wrote:
> 
> On Wed, Feb 28, 2001 at 03:16:56PM -0800, Peter Badovinatz wrote:
> 
> > but we still have to agree as to the positions or layout.  We also
> > usually support (in fact usually demand to eliminate single points
> > of failure) each node have multiple network connections, and
> > multiple names, so a single hostname is not sufficient for us.
> 
> I thought that in most HA clusters, each machine has a "true name" (&
> IP) that's unique and never changes, and then other names (& IP
> addresses) that are associated with services that move around when
> things fail?

Generally that's the model.

> A single, unique hostname is still sufficient, and you
> can make them one byte. Then you don't have any need for an extension?

Making things one byte long is not useful for large clusters and unaesthetic
to say the least.

One can give one's nodes names.  One can number one's nodes a set of dense
node numbers.  There is a purpose to each.  Node numbering typically needs
to be dense.  Node names typically need to be permanent (for tracking
failures, etc).

Here's why one might want a dense set of integral node numbers:
Sending around bitmaps for determining cluster membership.

Here's why one migh want node names:
A permanent name for a node which persists as you add and delete nodes to
the cluster and allows you to track what's on the given node over time.  So,
if you see that you've had 3 crashes on node foo, that it's always been the
same computational unit, and not 3 different ones (which could happen if one
adds or deletes nodes to the system).

So, it seems pretty clear to me that one wants both node names and node
numbers, and a canonical way to refer to a node in either domain.

Then the question comes up:
Which way do you refer to the node in which context, and how do you get from
one domain to the other?

	-- Alan Robertson
	   alanr@unix.sh

Linux-cluster: generic cluster infrastructure for Linux
Archive:       http://mail.nl.linux.org/linux-cluster/