[squid-users] How do I permanently save cache files?

[ql li]

Save the new file overwrites the file cache after some time.
My configuration:
cache_mem  3 MB
http_access allow all
acl PKG urlpath_regex \.pkg
cache deny !PKG
refresh_pattern -i \.pkg$ 52560 100% 525600 ignore-reload
#refresh_pattern . 525600 0% 525600 ignore-reload
cache_effective_user squid squid
logfile_rotate 0
maximum_object_size_in_memory 1024 KB
maximum_object_size 5 GB
max_filedesc 65000
cache_dir ufs /mnt/sda1/squid 20480 16 32
quick_abort_min -1
#quick_abort_max -1
range_offset_limit -1
#quick_abort_pct -1
logfile_daemon /dev/null
via off
forwarded_for transparent

squid runs openwrt router