DNS caches that support partitioning ?

[fw at deneb.enyo.de (Florian Weimer)]

* John Levine:

> Are there DNS caches that allow you to partition the cache for
> subtrees of DNS names?  That is, you can say that all entries from
> say, in-addr.arpa, are limited to 20% of the cache.

You can build something like that using forwarders and most DNS
caches.  But it won't result in an exact split because cross-subtree
CNAMEs and DNS delegations will cause caching outside the subtree.
However, for in-addr.arpa, that's probably what you want anyway.