SUMMARY II Using cachefs as a fail-over mechanism

From: Brett Lymn (
Date: Fri Aug 11 2000 - 00:50:57 CDT

After a bit more research I have found that Sun have already done what
I want, I thought I would share it :-)

>Now my dilemma is do I want to script the clients to check if the
>filesystem is available and force a refresh periodically OR script the
>server to distribute the files out somehow. I am leaning towards
>scripting the clients on the basis that a server push is prone to a
>machine getting dropped off the list and losing updates.

I was searching the sunsolve patch database for patches for cachefs
and I turned up infodoc number 21701 which describes running cachefs
in "disconnected" mode.... JUST WHAT I WANTED. There is an option
that is not documented in any man pages I saw called "disconnectable"
which allows the cachefs to serve files even if the back filesystem
server is down. There is a daemon (cachefsd - no man page for that)
that monitors the connection and resolves any changes between the back
filesystem server and the cache when the server comes back on line.
So that makes the choice easy for me. I can simply do this:

mount -F cachefs -o backfstype=nfs,cachedir=/opt/cache,ro,disconnectable,local-access miscsan:/ /opt/test

to make my systems ride out any outage on my file server.

Brett Lymn, Computer Systems Administrator, BAE SYSTEMS

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