[Spambayes] Sharing database among multiple IMAP clients?

[Deneb Meketa]

Hello!  I'm completely new to SpamBayes, and I'm trying to figure out
how I want to set it up for myself.  Thanks to the list in advance.

I'll probably be using an IMAP server and accessing my mail from two
main places - work and home.

My question is: how can I (and should I, even) share the training data
between the two locations?  Ideally I'd like to maintain just one
database, since this will all be a single set of mail; otherwise I'd
have to repeat the same training at home and at work.

Several possibilities occur to me, and I'm curious to hear other users'
suggestions on these:

1. Manually copy the database file(s) from one location to the other.
There are several variations on this.  I could just do the initial
training in one location and copy to the other, then maintain each
database separately thereafter, expecting the follow-on training to take
much less work.  Or I could copy the DB each time I did some training.
Or, if there's some reliable way to merge the two slightly different
DBs, I could periodically do that.

2. Maintain the database file(s) on a server somewhere.  This is really
more what I want, but it's harder to arrange.  The best thing,
obviously, would be to run SpamBayes on the server, but I'm expecting
that, for reliability and simplicity, I'll probably be using a shared
commercial server where I can't install SpamBayes.  But even if I'm
running SpamBayes on the client, I could maintain a single DB in some
online location.  I could stick it on an FTP or rsync server, and have a
script (or maybe even write a SpamBayes extension) that downloads it
when I begin using SpamBayes and uploads it when I'm done.  I could
store the DB at work and map a Windows network drive to point at my work
machine through my VPN, and configure SpamBayes at home to use the DB on
the network drive - but my VPN isn't completely reliable, so that could
be a hassle.  Or perhaps there are distributed-DB features built into
some of the storage options that SpamBayes can use?

3. Carry a little USB drive around with me, and keep the DB on that.
(Does the DB get too big for this to be practical?)

4. Super Crazy Ninja Trick?: enhance the SpamBayes IMAP proxy with the
ability to maintain a DB in a folder on the IMAP server, download it
before beginning filtering, and upload it whenever it is modified.  If
this seems productive, and the feature doesn't yet exist, I'd be happy
to add it if I can find the time.

Surely others have run into the same DB-replication question.  Is there
any conventional wisdom on this yet?  I didn't find anything obviously
related in the wiki, the FAQ, or the mail archives.  I realize the
question probably does come down to a simple issue of "how do I share a
file between multiple sites?", which isn't particular to SpamBayes, but
maybe SpamBayes users are a good crowd to ask such a question of.

Any help is much appreciated!

Best,
Deneb Meketa,
San Francisco.