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- Our DNS servers run PowerDNS. We use geographical DNS to distribute requests between our two main sites (US and Europe) depending on the location of the client.
- We use LVS on commodity servers to load-balance incoming requests. LVS is also used as an internal load balancer to distribute MediaWiki and Lucene backend requests. For backend monitoring and failover, we have our own system called PyBal.
- For HTML we use Squid and Varnish caching proxy servers in front of Apache. For image files, we use Squid/Varnish in front of Sun Java System Web Server.
- All our servers run Ubuntu Linux, except for the image file storage servers which run Solaris.
- Our main web application is MediaWiki, which is written in PHP.
- Our structured data is stored in MySQL. We group wikis into clusters, and each cluster is served by several MySQL servers, replicated in a single-master configuration.
- We use memcached for caching of database query and computation results.
- For full-text search we use Lucene, with extensive customisations contributed by Robert Stojnic.
- http://noc.wikimedia.org/conf/ - Wikimedia configuration files
For a list of servers, please see server roles.
As of June 2010, we have four colocation facilities:
- Hostway (formerly PowerMedium) in Tampa, Florida.
- Equinix (formerley Switch and Data) in Tampa, Florida.
- Kennisnet in Amsterdam, the Netherlands.
- EvoSwitch in Amsterdam, the Netherlands.
The backend web and database servers are divided between our two Tampa facilities. At EvoSwitch, we have a Squid cache cluster and several miscellaneous servers. The Kennisnet location is now used only for network access and routing.
EvoSwitch and Kennisnet are recognised as benefactors for their in-kind donations. See the current list of benefactors.
As of 2012 there are also servers in Ashburn, Virginia (eqiad)
While Wikipedia is free in both the "free speech" and "no charge" senses of the word, running the web site does cost money. You can help with purchasing new server hardware by donating to the non-profit Wikimedia Foundation: http://wikimediafoundation.org/wiki/Donate
Status and problems
You can check one of the following sites if you want to know if the Wikimedia servers are overloaded, or if you just want to see how they are doing.
If you are seeing errors in real time, visit #wikimedia-tech on irc.freenode.net. Check the topic to see if someone is already looking into the problem you are having. If not, please report your problem to the channel. It would be helpful if you could report specific symptoms, including the exact text of any error messages, what you were doing right before the error, and what server(s) are generating the error, if you can tell. The #wikipedia channel may be better populated and the topic there may contain more updated information about the status of the problem. (But this channel is for general conversation about Wikipedia.)
More hardware info
- Technical FAQ - How about the hardware?
- Your donations at work: new servers for Wikipedia, by Brion Vibber, 02-12-2009
- Server admin log - Documents server changes (especially software changes)
Offsite traffic pages
Out of date information
Useful information about other sites
- Evolution of LiveJournal systems:
- Google cluster architecture (PDF)
- MySQL User's Conference 2004 blog highlights