What happens when a mongrel_cluster starts?

My server is running in a node in www.linodes.com, so it is not a fast
server.

I have a mongrel cluster with 3 instances. When I do a
mongrel_cluster start, the 3 mongrel_rails instances churn at 15-20%
CPU for about 4 mins before they are initialized. The pid files are
not written until this 4 mins is completed.

In those 4 mins, all calls to the server seem to hang.

What happens in those 4 mins? What all happens when a rails instance
is started through mongrel_cluster? Of course, I don't see this on my
fast development machine.

Any guidance would be appreciated.