[Zope] ZTables and/or Catalog plugable brains?

[Jay, Dylan]

I'm in the process of of write a zope product that will deal with a lot
numerical data (records with a few ids and a few float values). Rightly or
wrongly (comments welcome) I've decided to do this inside the ZODB rather
than rely on a relation database. This is largely because this data will 

- not be high-write
- I want to do processing on all this of this data on multiple servers
- and I am presuming that at some point in the not too distant future zope
will let me replicate this data very easily to make it even more highly
available.

I tried using ZClasses but it seems to run slow and take up space. Instead
I'm  using Catalog (without ZCatalog) to contain the data. I'm presuming
this will be quite efficient (comments welcome).

Now to my question, How do Catalog plugable brains work? I've looked but
can't see what the brain class has to look like to work. My first attempts
don't seem to work. The classes are created but don't contain the data. Is
the record data passed into the constructor?

Also in my searches I came across lots of references to something called
ZTables. This seems to be a Catalog with a UI that is about lots of tabular
information (rather than a ZCatalog which is specialized to replicating and
indexing existing objects). Is this dead? If not where is it? If so, why? It
seems like a really good idea to me. It seems to be there are times when
objects (esp ZClasses) are too heavy? 

Anyone with comments about how ZPatterns fits into all of this would also be
welcome.