[Federated-fs] Conf call 6/5/2008

[Robert Thurlow]

Everhart, Craig wrote:
> I *totally* agree with Dan's bias on this.  It's a surprise to me that
> others thought that there was a "namespace" that existed independently
> of the file systems that make it up.
> 
> What is the relationship between path data that exists both in a fileset
> (in a file server--Dan's #1 case) and in the NSDB and (as in Paul's
> addendum to Dan's #3) all the instances of the parent path data that are
> subsidiary filesets?  Is there some authoritative copy with the others
> just hints?  What is the replication protocol by which path data is
> propagated?  How consistent does it have to be?
> 
> If we were stumbling thinking about the constraints on fileset
> replication and consistency, why would this be a simple answer?  Right
> now it's an unmotivated, underspecified, and unconstrained additional
> criterion for any implementation.  (And them's its good points...:-})
> 
> If others (Paul? Renu?) feel like this needs to be changed, could they
> do it with a more fleshed-out proposal?

I don't want to keep a copy of all of the mapping data
(with or without authority) in the NSDB, either.  But I
do wonder if the motivation is something like this:

I want an admin application that can show me the whole
namespace.  I want to be able to browse it like a Google
map, going up/down, left/right in the global directory
tree.  I'd like to see which nodes are junctions, and to
be able to click on them and see the details about their
replicas.  In the fullness of time, I'd like to be able
to click on a point in the namespace and select an option
to make that point a separate, replicated filesystem, and
to adjust the characteristics of existing filesystems.

Now, if all we have is a way to drill down from the top
of the namespace for any particular path, this could be
bloody hard.  Having more information would help.  An
alternate question is, where could we get more info?

One suggestion is that the protocol permit a query to
an NFS server participating in the namespace, to list
the junctions in a particular filesystem.  If we could
start at the top, find the Nth level filesystems and
ask them what junctions point outside of the filesystem,
we could enumerate the namespace far quicker.  We would
still have to send packets all over the place - "find
the root" DNS queries, NSDB lookups, NFS accesses and
whatever we use to enumerate junctions in a filesystem -
but I have always expected that.

Does this shed light or kick up dust? :-)

Rob T