: Wikipedia probably counts as having a "huge website", even if it's still tiny compared to, say, Google. You can find a description of their server architecture here. Basically, their SQL backend

@Phylliss660

Wikipedia probably counts as having a "huge website", even if it's still tiny compared to, say, Google. You can find a description of their server architecture here.

Basically, their SQL backend consists of a bunch of clusters, each one consisting of a single MySQL master server whose data is replicated to a bunch of read-only slave servers. Also, images and revision text, which make up the bulk of the data and are essentially immutable once written, are stored separately.

Each of the various Wikimedia sites runs on a specific cluster. English Wikipedia, the largest of them by far, has a separate cluster all for itself, while most of the other sites store their data on shared clusters.

In addition to within-cluster replication, the databases are also replicated to servers running in remote data centers, although I believe that this is currently mainly used for live offsite backups and for the Wikimedia Toolserver (a separate set of servers for community-developed tools) which is hosted in Amsterdam, on the other side of the Atlantic from the main DB clusters in the U.S.

Here's a diagram of the Wikimedia server layout from 2010:


For more up-to-date information, see this presentation from last month.

A notable feature of the server layout is that the database servers run behind a veritable army of load-balanced web servers, which themselves are hidden behind a whole bunch of caching proxies. Thus, most requests from random visitors browsing Wikipedia never even hit the webservers, much less the database.

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