“We currently have some room to grow but we’ll be expanding to a larger space in the coming months to fit the new growing infrastructure,” said Scott Baker, Digg’s VP of Operations. “We are always expanding our infrastructure to meet the demands of higher traffic and new features that we’re always developing.”

The company’s short-term goal is to refine its data center architecture to serve content from two locations, rather than just one. “We are currently in two data centers set up in an active/passive configuration for disaster recovery purposes,” said Baker. “Part of this expansion is to make better use of our (backup) data center installation. We are working towards some site rearchitecture to allow us to have an active/active setup with traffic being served from both locations simultaneously.”

Digg isn’t the first social media site to pursue this capability. Facebook recently added a second data centersite in Virginia to its original facility in Santa Clara, Calif. and reworked its architecture to take advantage of its bi-coastal infrastructure. “The primary reason for building a new datacenter on the East coast was latency,” Facebook engineer Jason Sobel wrote about the move. “By putting servers in Virginia we could reduce the time to send a page to users on the east coast and in Europe by a noticeable amount.”

International expansion is a key component of Digg’s expansion, as about half of its 30 million existing users hail from outside the US. The site will also add greater personalization and additional content and categories. Helping to fund these initiatives is $28.7 million round in new funding, led by Highland Capital Partners.

That funding may also help with another infrastructure improvement: the use of a content delivery network (CDN). “We’re evaluating the use of a CDN for serving some of our more static content,” said Baker. CDNs like Akamai (AKAM) and Limelight Networks (LLNW) help sites improve their performance by storing content (caching) in a distributed network of data centers, moving content closer to users.

Digg’s primary data center is an Equinix facility in Silicon Valley. Digg CEO Jay Adelson was the founder and chief technology officer at Equinix as it built its network and reputation, and then joined with Kevin Rose to co-found Digg. The company added a disaster recovery site after a lengthy outage in June 2007.

Baker didn’t provide any details about the prospective locations and providers for Digg’s data center expansion. But given the companies’ shared lineage, Equinix is well-positioned to benefit from continued growth for Digg and its infrastructure. Equinix has recently expanded its data centers in Washington, New Jersey and Chicago and would have capacity available in key expansion markets. The company also has data centers in both Europe and Asia, which would allow it to support an international expansion or peering agreements in those regions.

For more on Digg and its infrastructure, see How Digg Works: A Look Under The Hood and our Digg Channel on DCK.

The social media site Digg is known for the huge volume of traffic it sends to sites that are linked on its front page. How does Digg manage its web site to support all that activity – 22 million users and 220 million page views in August, according to QuantCast)? Joe Stump provides an overview of How Digg Works in the first post on the Digg Technology Blog, which made its debut Thursday. An excerpt:

Ask Ron – our Systems Engineering Lead – the exact number of servers we have in production and he’ll probably respond with, “I don’t honestly know.” I can say we’ve got dozens of web servers and dozens more DB servers. I can say with certainty it takes six specialized graph database servers to run the Recommendation Engine and we have another six to ten machines that serve files from MogileFS. But really, the numbers are the least interesting part of the equation. What makes Digg an interesting place to work are what the pieces are and how they fit together.

Stump’s post shares some details on Dogg’s architecture and how the various pieces work together to process typical requests from Diggers like me.

Digg isn’t alone among social networking sites sharing information about their efforts on the back-end. The Engineering @ Facebook blog provides an inside look at some of the infrastructure challenges face by Facebook.

Or not. Execs from Facebook and Salesforce made an appearance at a Dell media event in San Francisco Tuesday, but there were no new partnerships or services announced. Facebook VP of technical operations Jonathan Heiliger spoke about the company’s operations, and commended Dell for being a “thought leader in large-scale infrastructure” and the most aggressive of the major server vendors in offering stripped-down cloud servers. We had assumed that the chumminess between Dell and Facebook was bad news for Rackable (RACK), which counts Facebook as its fourth-largest customer. But Heiliger made it clear that his appearance didn’t signify that Facebook necessarily favored Dell, and made a point of acknowledging other server makers, including Rackable. 

Heiliger has been broadly critical of server vendors for their focus on enterprise servers as cloud builders have emerged as a bigger chunk of the server market. The Wall Street Journal summarized Heiliger’s comments as he elaborated on this point Tuesday:

The social networking company, which has more than 10,000 servers from Dell and other providers, is tired of all the high-cost features companies pack into servers – on a slide, he pointed to extra USB ports and unnecessary graphics capabilities as examples. Most server makers are selling what, in automobile terms, would be the equivalent of a Lexus “at a Toyota price,” he said. What Facebook wants “is the Scion product at the Scion price.” He said Dell seems to be ahead of other server makers in selling inexpensive servers that reduce power and cooling requirement.

See additional coverage from Dan Farber, Om Malik and a video from Steve Gillmor at TechCrunch IT.

“The first pain point we hit was just database stuff. The first thing you’ll notice is when you start to grow these queries, the database can’t commit as much time to committing a certain query as it used to,” said Gorodetzky. “You’ll find the normal things that work, suddenly don’t. You’ll find that, one day, you’ll see a spike in your graphs telling you that something’s going slower. Once you do that, you get to the point where the database part is as fast as it can be, you cache things. You scale out your Web server so you have more resources there, generally caching and doing less work per request.”

Gorodetzky also talks about the challenges involved with image serving, especially the expanded use of thumbnails. The site runs on a LAMP stack (Linux-Apache-MySQL-PHP).

You can track what we’re up to at Digg here. If you’re interested in data center and cloud computing news, add us to your friend list. Also, if you haven’t yet seen System Management News, it’s definitely a read. One of its columnists is John Rath, who many of you may know from his Data Center Links blog.

“We’ve been working for several months on a full Disaster Recovery site for Digg,” co-founder Kevin Rose wrote on the Digg blog. “Once operational, our DR site will let us make site updates without interruptions – and in tonight’s case where things went haywire, you’d never know we were making updates at all.”

That’s an important goal for Digg users, some of whom tracked the downtime and some of whom expressed their distress – and naturally blogged about it and submitted the URL to Digg as soon as it came back online.

Digg houses its web servers at Equinix, a leading provider of network-neutral data centers and Internet exchange services. As traffic has scaled up, Digg has benefitted from Equinix’ peering infrastructure, which offers “immediate access to every major global network for the most efficient delivery of content to end-users.” Digg is housed in one of the company’s Silicon Valley data centers (Equinix doesn’t say which, remember the Fight Club rule).

Equinix has sturdy data centers that are located throughout the country, which should make it relatively simple for Digg to establish backup operations in another location. Companies seeking a disaster recovery solution typically locate their backup servers a significant distance from the primary data center, so a single major disaster (such as an earthquake in California) won’t knock both sites offline.

Digg and Equinix have a shared lineage. Jay Adelson was the founder and chief technology officer at Equinix as it built its network and reputation. Adelson then joined with Rose to co-found Digg, which has quickly become one of the web’s most popular destinations.

Oddly, Digg uses a proxy registration service, Go Daddy’s Domains by Proxy, Inc., to conceal the registrant information for digg.com and its other domains. It’s somewhat unusual to see proxy registration for corporate sites, which usually seek to build credibility through transparency. Just another sign that Digg doesn’t do things the old-fashioned way.

(Digg) is similar to how Equinix (eliminated intermediaries) for telecom companies. When the Internet became a commercial medium in 1994, all of the Internet had been funded and operated by the government and universities. When it switched over to one operated by telecommunication companies, a very strong hierarchy developed. Tier 1 ISPs, the top five players in the world, would collect a dime on every packet that flowed throughout the Internet. Part of the reason was all the Internet networks had to interconnect with each other using these antiquated network access points operated by carriers. Equinix replaced these single, network-owned facilities with Internet business exchanges where anyone could exchange packets with anyone in a neutral playing field. This allowed the dot-coms like Yahoo and Google and others to really exert their might. Digg does a very similar thing to the media.

For more, including Adelson’s thoughts about the recent “user rebellion” at Digg, read the entire interview.

Not so with Digg, which houses its servers at Equinix, a leading provider of network-neutral data centers and Internet exchange services. As traffic has scaled up, Digg has benefitted from Equinix’ peering infrastructure, which offers “immediate access to every major global network for the most efficient delivery of content to end-users.” Digg is housed in one of the company’s Silicon Valley data centers (Equinix doesn’t say which, remember the Fight Club rule).

Digg’s choice of Equinix is no shocker, as the companies have a shared lineage. Jay Adelson was the founder and chief technology officer at Equinix as it built its network and reputation. Adelson then joined with Kevin Rose to co-found Digg, which has quickly become one of the web’s most popular destinations. Adelson’s knowledge of Internet peering and traffic management – he was also a key player in the Palo Alto Internet Exchange (PAIX) before founding Equinix – made it a pretty safe bet that Digg would scale well if things took off. And they have, as Digg currently serves more than 8 million page views a day.

“The Digg community is constantly challenging us to do new things,” said Scott Baker, director of operations at Digg. “We need a data center environment that is flexible enough to accommodate our growth, yet is rock-solid reliable. Equinix has been a great partner for us.”

Equinix offers Digg immediate access to dozens of leading carriers, ISPs and network service providers within the same facility. By operating within this “Internet ecosystem,” Digg can link directly to other networks, rather than having to connect through multiple sites or run physical fiber connections over long distances. This direct connectivity provides improved performance by reducing bottlenecks in the path between content and end-users.

Digg can also implement peering relationships with the abundance of networks at Equinix. Peering is the fundamental process by which all Internet traffic – from email to video – is exchanged between the backbone networks that comprise the Internet. Networks that exchange equivalent amounts of traffic typically don’t charge one another for IP transit, offering substantial cost savings.

“The network and content interconnection and peering that Equinix facilitates enables companies such as Digg to conveniently leverage the cost reduction and performance benefits of direct interconnection to an aggregation of business partners in a single location,” said Margie Backaus, chief business officer of Equinix. “This peering infrastructure has become a strategic element in the operation of the Internet and it improves the performance for end-users by enabling data to pass from one network to another without intermediary networks or bottlenecks.”