Surviving Migration Plans

So there I was, listening to Seth Falcone (@ ErlangFactory) describe a fairly complex migration (CouchDB to MySQL, etc. etc.).  The theory was that this would take 3 hours - the reality came to around 3 days. 

Sounds like badness, right?
I say thee nay!

In my books, this was actually a pretty huge success - it actually worked.  And that, my friends, is a huge, huge win.  As Clausewitz (or Moltke?) said a while back, "No campaign survives contact with the enemy", and in this case, the enemy is Reality, which, my friends, is a harsh harsh mistress.

My point? 
One of the major advantages of The Erlang Way is that it significantly aids Tap Dancing Under Fire. 
Mind you, hot code-loading is probably one of the major advantages here - compile and deploy yer module without having to touch the vast majority of stuff thats out there, and It Just Works. (Incidentally, this is one of those things that you just don't get unless you do erlang.  Yes you can do it in Java, but man, is it ever complicated, and does it blow).
The other advantage, which is almost as cool, is the error log.  Face it, the odds are that your migration is failing, and you're spinning out error messages.  In erlang, your error log almost always tells you exactly whats wrong, as compared to java where your stack trace is just the beginning of your long nightmare.

So yeah, Erlang is A Good Thing, especially when you need to Migrate...