Squid Hardware Choices
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Sizing and scaling HTTP caches

• Examine three possible machine configurations using pc hardware.
  • High-End - A state of the art new machine
  • Mid-Range - One using relativly modern equipemnt
  • Low-End - The other, older generation pc server hardware

• High-end
  • AMD Athlon MP 2400+ (2ghz)
  • 2GB pc2100 ddr memory registerd, ecc
  • 4x Western digital 7200rpm ide drives 30GB
  • D-link gigabit ethernet copper
• Mid-Range
  • Intel PIII-850
  • 768MB PC100 registerd ecc sdram memory
  • Western Digital 8.4GB ide disk
  • 9GB Seagate barracuda ultra160 scsi disk
  • 2 x 18GB Seagate Cheetah x15 ultra160 scsi disk
  • Intel 82559 Pci 10/100 ethernet nic

• Low-End
  • Intel Pentium-Pro 200 processor
  • 128MB edo 60ns dram
  • Western Digital 2.5gb ide disk
  • Symbios 53c875 ultra-wide controller
  • 2 x Seagate hawk 2gb f/w disk (5400rpm)
  • 3com 905 10/100 ethernet nic

• Configuration Changes
  • High-End

         cache_mem  768 MB
         cache_swap_low  95
         cache_swap_high 98
         maximum_object_size 8192 KB
         cache_dir aufs /usr/local/squid/cache0 20000 128 256
         cache_dir aufs /usr/local/squid/cache1 20000 128 256
         cache_dir aufs /usr/local/squid/cache1 20000 128 256
         logfile_rotate 48
        

  • Mid-Range

          cache_mem  160 MB
          cache_swap_low  85
          cache_swap_high 95
          maximum_object_size 2048 KB
          ipcache_size 10240
          ipcache_low  90
          ipcache_high 95
          fqdncache_size 8192
        
          cache_dir diskd /usr/local/squid/cache1 17000 128 256 
          cache_dir diskd /usr/local/squid/cache2 17000 128 256 
    
          store_avg_object_size 40 KB
          buffered_logs on
          logfile_rotate 2
        

  • Mid-range

          cache_mem  16 MB
          cache_swap_low  85
          cache_swap_high 95
          maximum_object_size 2048 KB
          ipcache_size 4192
          ipcache_low  90
          ipcache_high 95
          fqdncache_size 3600
    
          cache_dir diskd /usr/local/squid/cache1 1600 128 256
          cache_dir diskd /usr/local/squid/cache2 1600 128 256
        

  • Both

          acl ourallowedhosts src 128.223.0.0/255.255.0.0
          acl mesd src 198.236.63.0/255.255.255.0
          acl owencache src 198.237.157.0/255.255.255.0
          acl owen srcdomain or.us
          acl lane srcdomain lane.edu
          acl orst src 128.193.0.0/255.255.0.0
          acl moaz src 205.167.77.0/255.255.255.0
          #Mike Schuch  
          acl lane-current src 163.41.60.128/255.255.255.128
          acl lane-future src 163.41.62.0/255.255.255.0
          acl all src 0.0.0.0/0.0.0.0
    
          http_access allow ourallowedhosts
          http_access allow mesd
          http_access allow owencache
          http_access allow owen
          http_access allow lane
          http_access allow orst
          http_access allow moaz
          http_access allow lane-current
          http_access allow lane-future
          http_access deny all
    
          icp_access allow ourallowedhosts
          icp_access allow mesd
          icp_access allow owencache
          icp_access allow owen
          icp_access allow lane
          icp_access allow orst
          icp_access allow moaz
          icp_access allow lane-current
          icp_access allow lane-future
          icp_access deny all
        

  • Mid-range

          cache_mem  16 MB
          cache_swap_low  85
          cache_swap_high 95
          maximum_object_size 2048 KB
          ipcache_size 4192
          ipcache_low  90
          ipcache_high 95
          fqdncache_size 3600
          
          cache_dir diskd /usr/local/squid/cache1 1600 128 256 
          cache_dir diskd /usr/local/squid/cache2 1600 128 256  
        

• Some numbers to think about - proxy.uoregon.edu (proxy1, proxy2)
  • 20,000 users
  • 6.5 Million object requests a day per box
  • Average object size ~40KB
  • ~20GB worth of traffic a an hours
  • 15Mb/s average, over 40Mb/s peak
  • with 36GB of storage (proxy1) over 40% cache hit-rate

• Rules of thumb
  • 10MB of ram required for every GB of cache dir
  • caching more than a day or two worth of objects proably isn't worthwhile
  • I/O is more imporant than cpu
  • lots of small disk are better than big ones, or raid stripes.

Joel Jaeggli joelja@darkwing.uoregon.edu - 06/11/2003