[OpenAFS] Using OpenAFS with Web Servers

Martin Schulz schulz@iwrmm.math.uni-karlsruhe.de
19 Mar 2002 08:51:42 +0100

"BNQ" <binq@yahoo.com> writes:

> This is exactly what I was thinking, but the problem is that replicas are
> not meant for files that are updated frequently (my clients are constantly
> updating files).

My feeling is that you should rather go for a real database for the
fast changing data (supposing you meant "webservers" by the notion of

N webservers writing to the same volume will *not* scale at all. 

N webservers writing to different volumes each should scale perfectly. 

N webmasters writing to M volumes should work as well. 

The replication of volumes is a kind of "push" channel. I think AFS
replication is well suited for essentially steady data. For the fast
changing data, rather look for a distributed database. I know that at
least Adabas D has such a feature, other products probably as well.

> Also I have a feel that the intranet bandwidth between the web servers and
> AFS servers are going to be a bottleneck.  I mean even a gigabit network
> will only take me so far.  Are these fears unfounded?

I think so. Make a statistic of what files get called regularly on
your webservers. You probably will find a rather small set that is
called very often and a large amount of seldomly accessed files. Now,
what files will be in your AFS client cache most of the time? 

> > Another great advantage is the ability to have a read/write staging copy
> > of web content where web developers can actively make changes, and then
> > atomically rolling those changes into production with one command.
> I did not know this was possible though AFS.  How would it be done?

You write to the read-write volume. These changes are only forwarded
to the read-only volumes by issuing a "vos release" command. Your
webservers should only access the read-only volumes: Voila!

Martin Schulz                             schulz@iwrmm.math.uni-karlsruhe.de
Uni Karlsruhe, Institut f. wissenschaftliches Rechnen u. math. Modellbildung
Engesser Str. 6, 76128 Karlsruhe