squid proxy big and small buckets not functioning correctly

I'm running the oneiric ppa version of orchestra on natty:
$ dpkg-query --show ubuntu-orchestra-provisioning-server squid
squid 2.7.STABLE9-2.1ubuntu6
ubuntu-orchestra-provisioning-server 2.21-0ubuntu1~ppa4

My /etc/squid/squid.conf file has the following diff against what is in current precise /usr/share/orchestra/conf/squid.conf [1].
$ diff -wu /tmp/squid.conf /etc/squid/squid.conf
--- /tmp/squid.conf 2011-11-07 08:59:51.732258352 -0500
+++ /etc/squid/squid.conf 2011-10-26 16:17:51.320501502 -0400
@@ -55,6 +55,8 @@
 extension_methods REPORT MERGE MKACTIVITY CHECKOUT
 hosts_file /etc/hosts
 coredump_dir /var/spool/squid
+
+# changes over /usr/share/orchestra/conf/squid.conf
 maximum_object_size 750 MB
 cache_dir aufs /var/spool/squid/small 40000 16 256 max-size=40M
 cache_dir aufs /var/spool/squid/big 40000 16 256

I did this:
sudo sh -c 'du -hs /var/spool/squid/small /var/spool/squid/big'
[sudo] password for smoser:
17M /var/spool/squid/small
186M /var/spool/squid/big

Then, did an apt-get dist-upgrade -d to precise and I see afterwards:
$ sudo sh -c 'du -hs /var/spool/squid/small /var/spool/squid/big'
[sudo] password for smoser:
17M /var/spool/squid/small
656M /var/spool/squid/big

The big dir grew significantly, while the small dir not at all.
It seems like our 2 directores are not functioning as they should, as clearly most of that 'apt-get dist-upgrade' would have been under 40M files.

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[1] http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/precise/orchestra/precise/view/head:/provisioning-server/usr/share/orchestra/conf/squid.conf