Database architecture for a multi-organization application

Hi All,

I am a newbie to RoR and to be honest web development in general, although I do have some experience of creating PHP and mySQL driven applications in the past.

Anyway at this stage I am still following relatively basic RoR tutorials but at the same time I am trying to envision how what I am learning relates to the eventual app that I want to create.

An area that I am struggling to envision right now is my eventual database architecture, and I was hoping that some of you could nudge my learning in the right direction.

So my app will be similar to basecamp I think in the sense that it will (hopefully!) be deployed to many organizations who will each have their own users, products, calendars, blogs and various other objects that are hosted in my database.

Now as I am reading these RoRs tutorials I can see how I would set this up where I have one big database for each of these objects and each one has some sort of organization key.

However even at this stage I am thinking that this will ultimately result in very large db tables where I could end up with presumably millions of rows and multiple users in different organizations all trying to read/write from the same table at the same time.

In short I am worried that architecting my app in this fashion could lead to a performance crash at some point (although this could be an unfounded worry on my part of course).

The other approach I could foresee is that for each organization entity I create individual db tables for their own users, products, etc. In other words this alternate approach would result in a very large number of smaller tables as opposed to a very small number of large tables.

One of the benefits I would see of this multi-table approach is that the number of users requiring simultaneous access to each table will be very small.

However my limited experience of RoR suggests to me that it is designed to work with the former architecture where I have large table behind each object type which has an 'organization' attribute.

Is this a valid conclusion and if so are my performance concerns unfounded?

Alternatively can you give me any pointers as to where I should take my RoRs learning to work out how to approach setting up a unique- database-per-organization architecture?

Many thanks in advance for your insight!