[squid-users] tuning an overloaded server

Hi,

I hope that someone can help me. I have 3 servers running squid acting as
a web accelerator for a single http server. I have been having a large
amount of problems with the http server locking up and having drive
failures and squid seems to be a great solution. I was pleasantly
surprised at the performance of squid when I first installed it. Even on
the slowest of my servers, it seemed faster than directly from the http
server, but after I put the load back on the slowest of my servers it was
0% idle. Since this server had a second hard drive that was basically not
being used, I moved the squid cache over to it. I then did some googling
and I made some other changes and the server is now only 0% idle a few
times a day. I am really suprised at just how tunable squid is and it was
wonderful that a change in configuration could make such a difference. But
since the busy season is coming, I still think that more can be done to
tune it.

Here are the changes that I made to the squid.conf:
redirect_rewrites_host_header off
acl all src 0.0.0.0/0.0.0.0
acl manager proto cache_object
acl localhost src 127.0.0.1/255.255.255.255
acl to_localhost dst 127.0.0.0/8
acl SSL_ports port 443
acl CONNECT method CONNECT
http_access allow manager localhost
http_access deny manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow all
icp_access allow all
http_port 80 accel vhost
cache_peer 10.10.1.4 parent 80 0 no-query originserver
hierarchy_stoplist cgi-bin ?
cache_mem 16 MB
maximum_object_size_in_memory 128 KB
memory_replacement_policy heap GDSF
cache_replacement_policy heap GDSF
cache_dir ufs /var/squid/cache 200 16 256
maximum_object_size 2048 KB
cache_swap_low 90
cache_swap_high 98
access_log /var/log/squid/access.log squid
cache_log /var/log/squid/cache.log
cache_store_log /var/log/squid/store.log
emulate_httpd_log on
buffered_logs on
acl QUERY urlpath_regex cgi-bin \?
cache deny QUERY
refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern . 0 20% 4320
acl apache rep_header Server ^Apache
broken_vary_encoding allow apache
half_closed_clients off
icp_port 0
log_icp_queries off
coredump_dir /var/squid/cache

Are there any other changes that can be made to improve cpu usage?

I also did an install from source, since I am using NetBSD systems I used
pkgsrc to install it. There are several build options:

arp-acl
aufs
carp
coss
diskd
icmp
ipf-transparent
pam-helper
pf-transparent
snmp
ssl
unlinkd

I looked up what some of these are, but I am not sure how they are used by
squid or if I really need them. My thought is that if I compiled squid
without these options it could improve performance. I wish there was more
information on running squid on BSD systems (especially recent info) and
then maybe I could be sure what effect compiling without an option would
have. For example, I know what pam is, but do I need it? I looked up what
unlinkd does and I can see it running, but will it help cpu usage to use
it? I don't see diskd running as a seperate process, so I don't know that
I am even using it. The only one that I am sure that I need is ssl.

Any help would be greatly appreciated!

Best Regards,
Al
Received on Fri Nov 21 2008 - 19:41:21 MST