For a very large network, it would make sense to configure a proxy server for every subnet and connect them to a parent proxy server, which in turn is connected to the caching proxy server of the ISP. To find the most appropriate server from which to request objects, a cache sends an ICP request to all sibling proxies.
The sibling proxies answer these requests via ICP responses. If multiple HIT responses were found, the proxy server decides from which server to download, depending on factors such as which cache sent the fastest answer or which one is closer. If no satisfactory responses are received, the request is sent to the parent cache. The more objects maintained in the network, the greater the possibility of finding the desired object.
Objects like these are not cached because they change each time they are accessed. To determine how long objects should remain in the cache, objects are assigned one of several states. Other headers specifying that objects must not be cached can be used as well.
Objects in the cache are normally replaced, because of a lack of free disk space, using algorithms such as LRU last recently used. This means that the proxy expunges those objects that have not been requested for the longest time. System requirements largely depend on the maximum network load that the system must bear. Therefore, examine load peaks, as during those times, load might be more than four times the day's average. When in doubt, slightly overestimate the system's requirements.
Having Squid working close to the limit of its capabilities can lead to a severe loss in quality of service. The following sections point to system factors in order of significance:. The amount of memory RAM required by Squid directly correlates with the number of objects in the cache. Therefore, it is very important to have sufficient memory for the Squid process, because system performance is dramatically reduced if the swap disk is used. Squid also stores cache object references and frequently requested objects in the main memory to speed up retrieval of this data.
In addition to that, there is other data that Squid needs to keep in memory, such as a table with all the IP addresses handled, an exact domain name cache, the most frequently requested objects, access control lists, buffers, and more. Squid is tuned to work best with lower processor core counts 4—8 physical cores , with each providing high performance.
Technologies providing virtual cores such as hyperthreading can hurt performance. To make the best use of multiple CPU cores, it is necessary to set up multiple worker threads writing to different caching devices.
By default, multi-core support is mostly disabled. In a small cache, the probability of a HIT finding the requested object already located there is small, because the cache is easily filled and less requested objects are replaced by newer ones. If, for example, 1 GB is available for the cache and the users use up only 10 MB per day surfing, it would take more than one hundred days to fill the cache. The easiest way to determine the necessary cache size is to consider the maximum transfer rate of the connection.
If all this traffic ended up in the cache, in one hour it would add up to MB. Assuming that all this traffic is generated in only eight working hours, it would reach 3. Because the connection is normally not used to its upper volume limit, it can be assumed that the total data volume handled by the cache is approximately 2 GB. Hence, in this example, 2 GB of disk space is required for Squid to keep one day's worth of browsing data cached. Speed plays an important role in the caching process, so this factor deserves special attention.
For use as a proxy server, hard disks with high rotation speeds or SSDs are the best choice. When using hard disks, it can be better to use multiple smaller hard disks, each with a single cache directory to avoid excessive read times.
Using a RAID system allows increasing reliability at expense of speed. However, for performance reasons, avoid software RAID5 and similar settings. File system choice is usually not decisive. However, using the mount option noatime can improve performance—Squid provides its own time stamps and thus does not need the file system to track access times. If not already installed, install the package squid. To ensure a smooth start-up, the network should be configured in a way that at least one name server and the Internet can be reached.
Problems can arise if a dial-up connection is used with a dynamic DNS configuration. If you want Squid to start when the system boots up, enable the service with systemctl enable squid. The output of this command should indicate that Squid is loaded and active running. The output of this command should be 0 , but may contain additional warnings or messages.
To test the functionality of Squid on the local system, choose one of the following ways:. To test, you can use squidclient , a command-line tool that can output the response to a Web request, similar to wget or curl. Unlike those tools, squidclient will automatically connect to the default proxy setup of Squid, localhost However, if you changed the configuration of Squid, you need to configure squidclient to use different settings using command line options. For more information, see squidclient --help.
The output shown in Example The example above contains two X-Cache lines. You can ignore the first X-Cache header. It is produced by the internal caching software of the originating Web server. IP address the client connected to [fast] acl aclname arp mac-address All Squid Configuration Options.
Restart Squid. Other Important File Locations for Squid. Even More Information about Squid. How Can We Help? Common Fixes Featured Articles Getting Started Other Products Cloud Sites 7. Managed WooCommerce Hosting Managed WordPress Security Bulletins Series Technical Support Tutorials InterWorx 2. Have Some Questions? Latest Articles. The Squid project provides a number of resources to assist users design, implement and support Squid installations.
Please browse the Documentation and Support sections for more information. Template customisation by Alex Dawson and Adrian Chadd.
Icons from Silk collection by Mark James of famfamfam. In this example it is set to weezie. For example, we will illustrate access by users of the Using the excellent access control features of Squid, you may configure use of Internet services proxied by Squid to be available only during normal business hours.
In those cases you should move and adapt your configuration accordingly.
0コメント