Clustering with FreeBSD

Andy Sporner asporner at
Tue Feb 10 10:17:43 PST 2004


> Is FREP avalaible somewhere? I'd love to bang on it.
> Remote Raw
> Devices would be cool, but if there's an easy way to
> sync individual
> files, that would do a good job too.

The "Proof of concept" which is weak compare to the
current version is available on my site at

> How does FREP figure out what files need to be
> synced (walking the tree isn't exactly fast for big)
> servers...)?

That is clear.  It is kind of a "throwback" to my
Commodore Vic-20 days (no floppys! Tape! and 3K!)
where you made a "wedge" when you wanted some kind
of special behaviour.   In this case I patched a
couple of files (kern/vfs_syscalls, kern/vfs_vnops)
whereby I watch for activities on files living in
directories.  Before each write operation I check
to see if it is a "controlled" file and if so I 
secure a lock against it from the cluster monitor,
meanwhile writer blocks until the grant (or it times
out with a failure).  When the write completes, it
goes to the other node(s) and the lock is released.

SO far I have been testing the concept without the 
locking and it is not too bad, but there are MANY
opportunities for improvement (more assync for the
UDP datagrams that are carrying the traffic).  I 
really need to find out the performance of the
That is where I am really concerned.  The Network
Traffic be scaled with multiple links sending data
(a feature from the clustering software)

I feel that this is the right place to put the 
intercepts in the kernel.  Otherwise with just 
a remote raw device you don't get over the filesystem
cache problems.  In this way it is handling the
problem through the front door, rather than the
back door.  It has it's costs--that's clear, but
I think the benefits are also clear. There are 
probably optimizations for the user-space code to
delay certain activities and to "lease" locks for
periods of time (that is already there but only

The available version the above links lack many things
and is "NOT to be taken seriously" for high-end 
applications.  There were some early testers and
I got some very positive feedback (as with this time)
and I have taken many of the suggestions in this 

In the next days I will put the "independant" version
of the new FREP on my server. Same place (As the
Germans say, "Same procedure this year--same procedure
ever year" (a reference to "Dinner for One").  Look
for this on Friday.  The complete version I will
put up some time later (as I have time to get it
more or less working).




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