Editing Web server (section)

==== File cache ====
Historically, static contents found in [[Computer file|file]]s which had to be accessed frequently, randomly and quickly, have been stored mostly on electro-mechanical [[Hard disk drive|disk]]s since mid-late 1960s / 1970s;  regrettably reads from and writes to those kind of [[Peripheral|device]]s have always been considered very slow operations when compared to [[RAM]] speed and so, since early [[Operative system|OS]]s, first disk caches and then also [[Operating system|OS]] file [[Cache (computing)|cache]] sub-systems were developed to speed up [[Input/output|I/O]] operations of frequently accessed data / files.

Even with the aid of an OS file cache, the relative / occasional slowness of I/O operations involving directories and files stored on disks became soon a [[Bottleneck (software)|bottleneck]] in the increase of [[#Performances|performances]] expected from top level web servers, specially since mid-late 1990s, when web Internet traffic started to grow exponentially along with the constant increase of speed of Internet / network lines.

The problem about how to further efficiently speed-up the serving of static files, thus increasing the maximum number of requests/responses per second ([[#requests per second|RPS]]), started to be studied / researched since mid 1990s, with the aim to propose useful cache models that could be implemented in web server programs.<ref name="ws-file-cache-mmc">{{Cite web|url=https://www.ra.ethz.ch/cdstore/www5/www218/overview.htm|title=Main Memory Caching of Web Documents|publisher=Computer networks and ISDN Systems|author=Evangelos P. Markatos|year=1996|access-date=2021-12-09|language=en|archive-date=20 January 2023|archive-url=https://web.archive.org/web/20230120185224/https://www.ra.ethz.ch/cdstore/www5/www218/overview.htm|url-status=live}}</ref>

In practice, nowadays, many popular / high performance web server programs include their own ''[[Userland (computing)|userland]]'' '''file cache''', tailored for a web server usage and using their specific implementation and parameters.<ref name="ws-file-cache-iplanet">{{Cite web|url=https://docs.oracle.com/cd/E19146-01/821-1827/gaidp/index.html|title=IPlanet Web Server 7.0.9: file-cache|publisher=Oracle|author=|year=2010|access-date=2021-12-09|language=en|archive-date=9 December 2021|archive-url=https://web.archive.org/web/20211209175035/https://docs.oracle.com/cd/E19146-01/821-1827/gaidp/index.html|url-status=live}}</ref>
<ref name="ws-file-cache-apache">{{Cite web|url=https://httpd.apache.org/docs/2.4/mod/mod_file_cache.html|title=Apache Module mod_file_cache|publisher=Apache: HTTPd server project|year=2021|access-date=2021-12-09|language=en|archive-date=9 December 2021|archive-url=https://web.archive.org/web/20211209194811/https://httpd.apache.org/docs/2.4/mod/mod_file_cache.html|url-status=live}}</ref>
<ref name="ws-file-cache-servez">{{Cite web|url=https://www.gnu.org/software/serveez/manual/html_node/HTTP-Server.html|title=HTTP server: configuration: file cache|publisher=GNU|year=2021|access-date=2021-12-09|language=en|archive-date=9 December 2021|archive-url=https://web.archive.org/web/20211209173634/https://www.gnu.org/software/serveez/manual/html_node/HTTP-Server.html|url-status=live}}</ref>

The wide spread adoption of [[Redundant array of independent disks|RAID]] and/or fast [[solid-state drive]]s (storage hardware with very high I/O speed) has slightly reduced but of course not eliminated the advantage of having a file cache incorporated in a web server.