Large Cache Tables - Is this going to be a problem?

Hello.

Background

We are a small web team who help mainly mom and pop type business get onto the net.

We are fairly new to drupal, but have built perhaps 80 or so sites with drupal. These are all mainly smaller websites (A few hundred pages at most).

A few clients also want us to help them convert some larger static websites into drupal. These probably have a few thousand pages at the moment and the sites get approximately 50,000 to 100,000 unique visitors a month.

Large cache files & limited disk space

One are that is concerning us is the large cache files/tables that drupal creates. Most of these sites have limited hard drive space. Perhaps 200mb up to 500mb.

In some cases some of these cache tables take up half the allocated disk space.

I have searched around on the forum for a while now, trying to get some definitive guide on caching and table sizes.

How do we manage the problem of large cache tables?

Basically, I want to understand this a little more before converting some of the larger sites over to drupal. I don't want the problem to arise of sites freezing/crashing because there isn't enough disk space available.

Is this something we would have to constantly monitor or are there any automatic drupal adjustments we can make to each site?

Why do the cache tables get so large?

It seems a little strange to me to have such large cache tables, which are way, way bigger than the actual content pages themselves.

Our server resources are currently limited and as we expand we will upgrade etc.

For each site at the moment we simply set the various out of the box caches on the admin/settings/performance page. We will probably start using the Boost module too and I presume this will create a large cache fiile too.

What can we do?

So is there some lower level performance recommedation or best practice suggestions somewhere regarding caching and database management etc?

I hope my questions make sense.

Thanks,

Colin