Joerg Schilling wrote:

>>> Do you see a benefit from replacing technology that is known since more 
>>> than 20 
>>> years by something that does not yet have even test users?

> Which benefits?

Caveat - this is about a follow-on case.

I'm glad you asked.  The current automounter hasn't had a decent
amount of work on it for years now, and it has a lot of issues,
strictly as a piece of code in a Solaris system.  Maps are read
on system reboot or at the request of an admin on each client,
so new filesystems or changes to locations are not picked up well.
Further, unmounts are often necessary to react to changes; this
causes the most pain in /net paths.  If there's a problem with
your network at boot time, you can run without maps or with
partial maps until someone notices and manually intervenes.
I'm the primary contact on automounter maintenance at Sun these
days, and as much as I rely on it, I'm aware of it's warts.

As a concept, there are more issues.  Autofs requires that an
admin edit a flat file of path-to-location relationships and
store them one of several network services, and the propagation
is widely variable.  Automounter maps are not standardized, so
multi-platform support is still dodgy.  And among implentations
compatible with Sun's map format, there are variations in what
features work that often mean you have to dumb down to the
lowest common denominator.  And despite the admin's work, all
clients can doctor their maps so that they see different paths
to files than their cube-mate does.

NFS referrals are baked into two standards (RFC3530 and the
not-yet-numbered NFSv4.1 spec), and are a way to redirect the
client to another place based in information at the server.
FedFS is a standard-in-development in the IETF's NFSv4 working
group, and ties well with NFSv4.0 and v4.1.  It builds a
server-side infrastructure to let servers return a coherent
set of referrals to clients.  It permits an admin to specify
a detailed set of locations, with enough metadata to permit
a V4.1 client to understand all the ways it can talk to a
multi-homed server, how old the different copies of data are,
and whether or not filehandles and state might be preserved
after a live migration has happened.  Each referral can be
managed in LDAP as a distinct thing, rather than as part of
a map, but are set-and-forget unless you need to change them.
Changes to the namespace should be visible far more quickly.
There's also a way to have a zero-admin client find the top
of a namespace - it will ask for a DNS RR to get started.
FedFS is also trying to be expandable enough to provide SMB
referrals to those other clients.

Bottom line: we think admins will be able to create uniform
namespaces for all of their clients across their whole company,
something that has always eluded us with the automounter.

Rob T

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