Martin Marji Cermak wrote: > I have been playing with Squid under a heavy load and there are some > stats. I am trying to maximise the "Byte Hit Ratio" value. I got 13% > average, but I am not happy about this number - I want it higher
To increase your byte hit ratio, you can: 1) Switch to one of the heap cache replacement policies 2) Tune your refresh_pattern settings to make Squid cache more aggressively See the FAQ and default squid.conf for details on these items. However, before going through the tuning, run an analysis tool (such as Calamaris) on your logs to see what your traffic pattern is like. This will show you what a reasonable byte hit ratio would be. If, for example, 70% of your traffic is dynamic content (which usually cannot be cached), then a 13% byte hit ratio is actually pretty good. > USED HARDWARE: > Processor:�����P4�1.8GHz > Memory:��������1�GB > Hardisk:�������40�GB�IDE�7200rpm > Requests: 180 req/sec (peak), 60 req/sec (day average). According to posts from Squid developers, a single caching Squid box has an upper limit of about 300 - 400 requests/second. This isn't too bad, considering you are using a single IDE disk for the entire system. > maximum_object_size 51200 KB (SHOULD I MAKE IT HIGHER ???) Actually, you might want to make it lower. Most web requests will not be for 50 MB files, and your byte hit ratio will be hurt if a 50 MB file that is requested once forces out fifty 1 MB files that are accessed twice each. The default is generally acceptable, unless log analysis shows large numbers of requests for larger files. > cache_dir aufs /cache 25000 16 256 You should size your cache to hold about a week's worth of traffic. Just watch your memory usage (1 GB of cache ~ 10 MB of memory for metadata). > cache_mem 8 MB This is generally fine - the OS will generally use free memory to cache files anyway, which will have the same effect as boosting this setting. > I am going to install a new box with SCSI disks so I will report to you > how the performance will change. Best disk performance will be achieved with multiple small, fast SCSI disks dedicated to Squid's cache, each with its own cache_dir (no RAID), and round-robin between the cache_dirs. Adam
