Hi to all squid users! I'm new to this list so please hold the big guns. Here's my setup: 1. Using Squid squid-2.6.STABLE6-5.el5_1.3 (pinned at this version since all newer ones will eventually stop responding with 100%cpu. But this could be the subject of another post on this list) 2. 2 servers in a heartbeat cluster. 192.168.2.1-2 are the IPs used for the internal communication in the cluster. 3. The requests come to Apache server who passes them to squid on the localhost. 4. The squids are configured to use the other squid as sibling and webserver instances from both servers as parents. ICP is used in all cases (the webservers will always reply MISS but the fastest to reply to ICP is probably the less busy and closest) My squid config looks like this: ******************************************************************** cache_effective_user squid cache_effective_group squid http_port 192.168.2.2:3128 transparent http_port 127.0.0.1:3128 transparent icp_port 3130 udp_incoming_address 192.168.2.2 cache_dir ufs /var/spool/squid 20000 16 256 cache_mgr webadmin@xxxxxxxxxxxxxxxxxxx visible_hostname host1.subdomain.domain.xx log_icp_queries on cache_access_log /var/log/squid/access.log cache_log /var/log/squid/cache.log cache_store_log /var/log/squid/store.log cache_store_log none emulate_httpd_log off cache_mem 512 MB maximum_object_size 100 MB # max cached object size maximum_object_size_in_memory 1 MB # max cached-in-memory object size acl all src 0.0.0.0/0.0.0.0 acl localhost src 127.0.0.1/32 acl localnet src 192.168.2.0/24 acl ssl_ports port 443 563 acl safe_ports port 81 80 443 acl zope_servers src 127.0.0.1 acl zope_servers src XXX.XXX.XXX.181 acl zope_servers src XXX.XXX.XXX.134 acl zope_servers src XXX.XXX.XXX.155 acl zope_servers src 192.168.2.0/24 acl manager proto cache_object acl connect method connect acl accelerated_protocols proto http acl accelerated_hosts dst 127.0.0.0/8 acl accelerated_hosts dst XXX.XXX.XXX.181/32 acl accelerated_hosts dst XXX.XXX.XXX.155/32 acl accelerated_ports myport 3128 acl purge method PURGE http_access allow zope_servers purge http_access deny purge http_reply_access allow all acl webdav method PROPFIND TRACE PURGE PROPPATCH MKCOL COPY MOVE LOCK UNLOCK never_direct allow all http_access allow manager localnet http_access allow manager localhost http_access deny manager http_access deny connect !ssl_ports icp_access allow localhost icp_access allow localnet http_access allow all cache_peer 192.168.2.1 sibling 3128 3130 name=theothersquid cache_peer 192.168.2.1 parent 8988 3988 no-netdb-exchange round-robin no-digest name=11 cache_peer 192.168.2.1 parent 8990 3990 no-netdb-exchange round-robin no-digest name=12 cache_peer 192.168.2.1 parent 8992 3992 no-netdb-exchange round-robin no-digest name=13 cache_peer 192.168.2.1 parent 8994 3994 no-netdb-exchange round-robin no-digest name=14 cache_peer 192.168.2.1 parent 8996 3996 no-netdb-exchange round-robin no-digest name=15 cache_peer 192.168.2.1 parent 8998 3998 no-netdb-exchange round-robin no-digest name=16 cache_peer 192.168.2.1 parent 9000 4000 no-netdb-exchange round-robin no-digest name=17 cache_peer 192.168.2.1 parent 9002 4002 no-netdb-exchange round-robin no-digest name=18 cache_peer 192.168.2.1 parent 9004 4004 no-netdb-exchange round-robin no-digest name=19 cache_peer 192.168.2.1 parent 9006 4006 no-netdb-exchange round-robin no-digest name=110 cache_peer 192.168.2.1 parent 9008 4008 no-netdb-exchange round-robin no-digest name=111 cache_peer 192.168.2.1 parent 9010 4010 no-netdb-exchange round-robin no-digest name=112 cache_peer 192.168.2.2 parent 8988 3988 no-netdb-exchange round-robin no-digest name=21 cache_peer 192.168.2.2 parent 8990 3990 no-netdb-exchange round-robin no-digest name=22 cache_peer 192.168.2.2 parent 8992 3992 no-netdb-exchange round-robin no-digest name=23 cache_peer 192.168.2.2 parent 8994 3994 no-netdb-exchange round-robin no-digest name=24 cache_peer 192.168.2.2 parent 8996 3996 no-netdb-exchange round-robin no-digest name=25 cache_peer 192.168.2.2 parent 8998 3998 no-netdb-exchange round-robin no-digest name=26 cache_peer 192.168.2.2 parent 9000 4000 no-netdb-exchange round-robin no-digest name=27 cache_peer 192.168.2.2 parent 9002 4002 no-netdb-exchange round-robin no-digest name=28 cache_peer 192.168.2.2 parent 9004 4004 no-netdb-exchange round-robin no-digest name=29 cache_peer 192.168.2.2 parent 9006 4006 no-netdb-exchange round-robin no-digest name=210 cache_peer 192.168.2.2 parent 9008 4008 no-netdb-exchange round-robin no-digest name=211 cache_peer 192.168.2.2 parent 9010 4010 no-netdb-exchange round-robin no-digest name=212 redirect_program /var/XXDIR/bin/squirm redirect_children 20 redirect_rewrites_host_header off acl static_content urlpath_regex -i \.(jpg|jpeg|gif|png|tiff|tif|svg|swf|ico|css|js|vsd|doc|ppt|pps|xls|pdf|mp3|mp4|m4a|ogg|mov|avi|wmv|sxw|zip|gz|bz2|tgz|tar|rar|odc|odb|odf|odg|odi|odp|ods|odt|sxc|sxd|sxi|sxw|dmg|torrent|deb|msi|iso|rpm)$ acl static_content urlpath_regex (.*)misc_/ExternalEditor/edit_icon$ acl static_content urlpath_regex (.*)p_/(.*) no_cache allow static_content acl post_requests method POST no_cache deny post_requests acl QUERY urlpath_regex \? acl CGIBIN urlpath_regex cgi-bin no_cache allow QUERY no_cache deny CGIBIN external_acl_type is_cacheable_type children=5 %{Cookie:__ac} %{Cookie:;__ac} %{Authorization} %{If-None-Match} /var/XXDIR/bin/squidAcl.py acl is_cacheable external is_cacheable_type no_cache allow is_cacheable no_cache deny all negative_ttl 0 refresh_pattern . 0 50% 999999 ignore-reload refresh_pattern -i /getFile$ 60 90% 3600 shutdown_lifetime 1 seconds pipeline_prefetch on ******************************************************************* The other squid will have a very similar config, just replace 192.168.2.1 with 192.168.2.2 and vice-versa. The main problem I'm facing is that every time the squid on the "passive" member responds with UDP_HIT the following line will be a TCP_MISS/504. Like this: 1286468808.210 0 192.168.2.1 UDP_HIT/000 168 ICP_QUERY http://127.0.0.1:3128/path/to/object - NONE/- - 1286468808.721 4 192.168.2.1 TCP_MISS/504 1915 GET http://127.0.0.1:3128/path/to/object - NONE/- text/html I've searched this list and internet in general for ideas of what I'm doing wrong and came up empty. I'm open to any suggestion for improvement in this setup. Performance is my main goal. Many thanks, Adrian