The information below is from a fantastic article from DataCenterKnowledge.com:
“How many servers does Facebook have? For some time now, the stock answer has been “more than 10,000 servers,” a number the company began using in April 2008. Facebook has continued to use that number, even as it has soared past 300 million users and dramatically expanded its data center space.
“Today we have somewhere in the neighborhood of 30,000 servers,” Rothschild said during the Q&A session following his talk, adding that the number ”will be different today than it was yesterday” because Facebook is adding capacity on a daily basis.
That places Facebook among the largest Internet companies that have publicly discussed their server counts, but still well behind hosting providers Rackspace, 1&1 Internet and OVH, which each house more than 50,000 servers in their data centers. See Who Has The Most Web Servers for more date on the largest infrastructures.
20,000 Servers In 18 Months
It also suggests that Facebook has added about 20,000 servers since early 2008, which explains why it borrowed $100 million in May 2008 to fund server purchases.
Rothschild also shared some huge numbers associated with Facebook’s photo storage operation, which now stores 80 billion images (20 billion images, each in four sizes). Rothschild said the real challenge isn’t storage, but delivery. ”We serve up 600,000 photos a second,” he said.
25 Terabytes of Log Data – Daily
The amount of log data amassed in Facebook’s operations is staggering. Rothschild said Facebook manages more than 25 terabytes of data per day in logging data, which he said was the equivalent of about 1,000 times the volume of mail delivered daily by the U.S. Postal Service.
Rothschild also discussed the effectiveness of the company’s engineering operations. Facebook currently has about 230 engineers on staff, who manage data for more than 300 million users. Rothschild said that ratio of one engineer for more than 1 million active users has been Facebook. ”We believe engineers at Facebook have a dramatic impact.””