Help: Expiring fragment cache across multiple domains

Hi All,

We have four domains setup for The Couch: thecouch.org.nz,
thecouch.co.nz, www.thecouch.org.nz and www.thecouch.co.nz. They are
all handled by the same rails app. The means that fragment caching
creates four folders in our cache directory, named after each URL.

This introduces two problems:

1: We are caching 4 times as much stuff as necessary
2: Our cache sweepers are only sweeping one of the caches (i.e. if we
login through thecouch.org.nz it sweeps thecouch.org.nz cache but not
the other 3)

I have tried making symbolic links for three of the folders pointing to
the main folder, but this didn’t work.

I would prefer not to have redirects setup for the domains.

Has anyone faced this problem before? Any suggestions?

Regards, Nathan