Mongrel Permissions and Cache

We’ve just started to implement page aching for our app, and it all
works fine on our development machines, but when we move to staging
there’s a problem, the cached don’t get written into the public
directory because Mongrel don’t have the right permissions (we’re
using Apache 2 and Mongrel Cluster). In fact it throws an error.
I’m not much of a sys admin so I can’t work out how to find out which
groups the Mongrels belong to and how to add them to a group that does
have permissions. Any help here would be greatly appreciated

Dale