- Our DNS servers run gdnsd. We use geographical DNS to distribute requests between our five data centers (3x US, 1x Europe, 1x Asia) depending on the location of the client.
- We use Linux Virtual Server (LVS) on commodity servers to load balance incoming requests. LVS is also used as an internal load balancer to distribute MediaWiki requests. For back end monitoring and failover, we have our own system called PyBal.
- For regular MediaWiki web requests (articles/API) we use Varnish caching proxy servers in front of Apache HTTP Server.
- All our servers run Debian GNU/Linux.
- For distributed object storage we use Swift.
- Our structured data is stored in MariaDB since 2013. We group wikis into clusters, and each cluster is served by several MariaDB servers, replicated in a single-master configuration.
- We use Memcached for caching of database query and computation results.
- For full-text search we use Elasticsearch (Extension:CirrusSearch).
- https://noc.wikimedia.org/ – Wikimedia configuration files.
As of May 2018, we have the following colocation facilities (each name is derived from an acronym of the facility’s company and an acronym of a nearby airport):
- Application services (primary) at Equinix in Ashburn, Virginia (Washington, DC area).
- Application services (secondary) at CyrusOne in Carrollton, Texas (Dallas-Fort Worth area).
- Caching at EvoSwitch in Amsterdam, the Netherlands.
- Caching at United Layer in San Francisco.
- Caching at Equinix in Singapore.
The backend web and database servers are in Ashburn, with Carrollton to handle emergency fallback in the future. Carrollton was chosen for this as a result of the 2013 Datacenter RfC. At EvoSwitch, we have a Varnish cache cluster and several miscellaneous servers. The Kennisnet location is now used only for network access and routing.
Ashburn (eqiad) became the primary data center in January 2013, taking over from Tampa (pmtpa and sdtpa) which had been the main data centre since 2004. Around April 2014, sdtpa (Equinix – formerly Switch and Data – in Tampa, Florida, provided networking for pmtpa) was shut down, followed by pmtpa (Hostway – formerly PowerMedium – in Tampa, Florida) in October 2014.
In the past we've had other caching locations like Seoul (yaseo, Yahoo!) and Paris (lopar, Lost Oasis); the WMF 2010–2015 strategic plan reach target states: "additional caching centers in key locations to manage increased traffic from Latin America, Asia and the Middle East, as well as to ensure reasonable and consistent load times no matter where a reader is located."
A list of servers and their functions used to be available at the server roles page; no such list is currently maintained publicly (perhaps the private racktables tool has one). It used to be possible to see a compact table of all servers grouped by type on icinga, but this is no longer publicly available. The puppet configuration provides a pretty good reference for software what each server runs however.
Status and monitoring
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.
- Icinga (private)
- Networking latency
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 Sustainability Initiative aims at reducing the environmental impact of the servers by calling for renewable energy to power them.
The Wikimedia Foundation's servers are spread out in five colocation data centers in Virginia, Texas and San Francisco in the United States, Amsterdam in Europe, and Singapore in Asia. As of May 2016, the servers use 222 kW, summing up to about 2 GWh of electrical energy per year. For comparison: An average household in the United States uses 11 MWh/year, the average for Germany is 3 MWh/year.
Only the few servers in Amsterdam run on renewable energy, the other use different conventional energy mixes. Overall, just 9% of Wikimedia Foundation data centers' energy comes from renewable sources, with the rest split evenly between coal, gas and nuclear power (34%, 28%, and 28%, respectively). The bulk of the Wikimedia Foundation's electricity demand is in Virginia and Texas, which unfortunately have both very fossil fuel heavy grids.
|Server name||Data center location||Provider||Date
energy consumption (kW)
|Energy sources||Carbon footprint (CO2/year)||Renewable
option and cost
|Equinix (Website)||February 2011||May 2016: 130
May 2015: 152
20% natural gas
|1,040,000 lb = 520 short tons = 470 metric tons
= 0.32 * 130 kW * 8765.76 hr/yr * 2.1 lb CO2/kWh for coal
+ 0.20 * 130 kW * 8765.76 hr/yr * 1.22lb CO2/kWh for nat gas
+ 0.25 * 130 kW * 8765.76 hr/yr * 0 lb CO2/kWh for nuclear
+ 0.17 * 130 kW * 8765.76 hr/yr * 0 lb CO2/kWh for renewable
|In 2015, Equinix made "a long-term commitment to use 100 percent clean and renewable energy". In 2017, Equinix renewed this pledge.|
|CyrusOne (Website)||May 2014||May 2016: 77
May 2015: 70
56% natural gas
14% wind (Oncor/Ercot)
|790,000 lb = 400 short tons = 360 metric tons
= 0.23 * 77 kW * 8765.76 hr/yr * 2.1 lb CO2/kWh for coal
+ 0.56 * 77 kW * 8765.76 hr/yr * 1.22lb CO2/kWh for nat gas
+ 0.06 * 77 kW * 8765.76 hr/yr * 0 lb CO2/kWh for nuclear
+ 0.15 * 77 kW * 8765.76 hr/yr * 0 lb CO2/kWh for renewables
2031 BE Netherlands
|EvoSwitch (Website)||December 2008||May 2016: < 10
May 2015: 10
|"a combination of wind power, hydro and biomass"||0||n.a.|
|ulsfo||San Francisco, CA
|UnitedLayer (Website)||June 2012||May 2016: < 5
May 2015: < 5
|25% natural gas
17% unspecified (PG&E)
|13,000 lb = 6.7 short tons = 6.1 metric tons (+ unspecified)
= 0.00 * 5 kW * 8765.76 hr/yr * 2.1 lb CO2/kWh for coal
+ 0.25 * 5 kW * 8765.76 hr/yr * 1.22lb CO2/kWh for nat gas
+ 0.23 * 5 kW * 8765.76 hr/yr * 0 lb CO2/kWh for nuclear
+ 0.36 * 5 kW * 8765.76 hr/yr * 0 lb CO2/kWh for hydro/renewable
+ 0.17 * 5 kW * 8765.76 hr/yr * ? lb CO2/kWh for unspecified
More hardware info
- Technical FAQ – How about the hardware?
- Your donations at work: new servers for Wikipedia, by Brion Vibber, 02-12-2009
- wikitech:Clusters – technical and usually more up-to-date information on the Wikimedia clusters
- Server admin log – Documents server changes (especially software changes)
Offsite traffic pages
- Cache strategy (draft from 2006)
- PHP caching and optimization (draft from 2007)
- Hardware orders up to 2007
Information about other web sites
- LiveJournal (livejournal.com):
- Google Search (google.com):
- See MediaWiki analysis, MediaWiki WMF-supported extensions analysis.
- "Wikipedia Adopts MariaDB — Wikimedia blog" (text/html). blog.wikimedia.org. Wikimedia Foundation, Inc. 2013-04-22. Retrieved 2014-07-20.
- Suffered a major DoS attack on September 6/7, 2019. See foundationSite:news/2019/09/07/malicious-attack-on-wikipedia-what-we-know-and-what-were-doing/.