[TriLUG] squid3 not caching large objects

[Kevin Otte via TriLUG]

I'm using a squid proxy on an Ubuntu 14.04 server to cache .deb packages
so I don't have to hit the Internet for all ~10 machines in the house.
Unfortunately, it doesn't seem to be caching packages larger than about
16MB. Since the kernel packages fall in this category, I'm not getting a
lot of the benefit.

My whole config:

root at atlantis:~# grep -v ^# /etc/squid3/squid.conf | tr -s "\n"

acl localnet src 172.31.2.0/23
acl localnet src fd60:e0:a0f4:100::/56
acl localnet src 2001:470:8:64f::/64
acl localnet src 2001:470:e203::/48
acl localnet src 2606:a000:a461:4500::/61   # TWC range, trusted portion
acl SSL_ports port 443
acl Safe_ports port 80          # http
acl Safe_ports port 21          # ftp
acl Safe_ports port 443         # https
acl Safe_ports port 70          # gopher
acl Safe_ports port 210         # wais
acl Safe_ports port 1025-65535  # unregistered ports
acl Safe_ports port 280         # http-mgmt
acl Safe_ports port 488         # gss-http
acl Safe_ports port 591         # filemaker
acl Safe_ports port 777         # multiling http
acl CONNECT method CONNECT
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost manager
http_access deny manager
http_access allow localnet
http_access allow localhost
http_access deny all
http_port 3128
cache_mem 128 MB
cache_dir aufs /var/spool/squid3 8192 16 256
maximum_object_size 512 MB
coredump_dir /var/spool/squid3
refresh_pattern ^ftp:           1440    20%     10080
refresh_pattern ^gopher:        1440    0%      1440
refresh_pattern -i (/cgi-bin/|\?) 0     0%      0
refresh_pattern (Release|Packages(.gz)*)$      0       20%     2880
refresh_pattern (\.deb|\.udeb)$   129600 100% 129600
refresh_pattern .               0       20%     4320
cache_mgr nivex at nivex.net
cachemgr_passwd [redacted] all


Hopefully extra eyes can see what I've missed.

Thanks,
Kevin