[Ruby] Activerecord for non sql backends

[Chris Ochs]

So just recently I lost the debate at work about using an rdbms versus 
starting out with a more scalable distributed system (I was for the 
former).  So now I'm doing some research to see if I can adapt 
activerecord to a non sql backend.  If not I'm probably going to suggest 
not even using rails, which I really hate to do.  Unfortunately the team 
I'm working with is more than happy to write their own web framework to 
keep their distributed storage system. 

The data store will be accessed through http calls, very similiar to 
what is already available in activeresource.  The transport layer is 
json (for now at least).  My first question is, outside of associations 
and the canned validations, what would I be missing by using 
activeresource instead of activerecord?  Would unit testing fly out the 
door also?

Secondly, if I give up too much by using activeresource, I'm considering 
ways to keep activerecord.  I was thinking of something like the 
tableless model together with a mixin to override methods such as find 
and save, which would connect via http to our backend services instead 
of going through the adaptor.

Thoughts, suggestions?

Chris