[OpenAFS] Openafs versions

[Benjamin Kaduk]

On Sun, 22 Mar 2015, huangql wrote:

> Hi Ben,
>
> Many thanks.
>
> Do the 1.4.14 and 1.6.11 File servers work together? Because I don't
> plan to upgrade all file servers at the same time.

Yes, they interoperate just fine.

To give a more detailed/pedantically correct answer, file servers register
themselves in the volume location database, but are otherwise standalone
entities; there is no real concern about version skew between a fileserver
and the database servers, since the RPCs that the fileserver uses to
register itself are unlikely to be removed (and must not be changed in a
backward-incompatible way).  The database servers, however, do a lot of
communicating amongst themselves, in particular via the ubik interface,
which presents a raw "disk" interface to the distributed database.  The
format of the data exchanged over this ubik interface is *not* guaranteed
to remain constant and compatible across major version changes; however,
there were no such changes between the 1.4 and 1.6 series, so running 1.4
and 1.6 database servers in the same cell is safe.  Version 1.8 is also
unlikely to introduce inompatible database format changes, but version 2.0
is expected to do so.

-Ben Kaduk