Facebook Technology Overview

Facebook had 22 Million active users in the middle of 2007; fast forward to 2011 and the site now has 800 Million active users, with 400 million of them logging in every day. Facebook has grown exponentially, to say the least! To cope with this kind of exceptional growth and at the same time offer a reliable and cost effective service requires out of the box thinking. Typical high-end, brute force, ultra redundant software and hardware platforms (for example Oracle RAC databases running on top of a few IBM Power 795 systems) won’t do as they're too complicated, power hungry, and most importantly far too expensive for such extreme scaling.

Facebook first focused on thoroughly optimizing their software architecture, which we will cover briefly. The next step was the engineers at Facebook deciding to build their own servers to minimize the power and cost of their server infrastructure. Facebook Engineering then open sourced these designs to the community; you can download the specifications and mechanical CAD designs at the Open Compute site.

The Facebook Open Compute server design is ambitious: “The result is a data center full of vanity free servers which is 38% more efficient and 24% less expensive to build and run than other state-of-the-art data centers.” Even better is that Facebook Engineering sent two of these Open Compute servers to our lab for testing, allowing us to see how these servers compare to other solutions in the market.

As a competing solution we have an HP DL380 G7 in the lab. Recall from our last server clash that the HP DL380 G7 was one of the most power efficient servers of 2010. Is a server "targeted at the cloud" and designed by Facebook engineering able to beat one of the best and most popular general purpose servers? That is the question we'll answer in this article.

Cloud Computing = x86 and Open Source
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  • jamdev12 - Thursday, November 3, 2011 - link

    I would definitely have to agree with you on this notion. HP servers are pretty expensive when you take into account 3 year warranties and 24/7 replacement options that going with a open compute server is a nice alternative to the "I can do everything" server. Better to stick to something you can do pretty well and efficiently than I can do many things poorly.
  • haplo602 - Friday, November 4, 2011 - link

    this is an option for somebody with a custom built infrastructure and dedicated DC services. however a general purpose server CANNOT do without.

    since the server category is different (general purpose vs custom built) the HP one does well (I'd say even excelent).
  • HollyDOL - Thursday, November 3, 2011 - link

    I would be quite interested how they determined Java and C# are 2/3x slower than C++. Since it seems pretty non-corresponding with reality to me. I have seen a few tests C++ vs. Java and the differences were in matter of %. As well as C# in my experience does the same jobs little bit faster than Java and the benchmark results generally confirm it.
    few links:

  • setzer - Thursday, November 3, 2011 - link

    I'm guessing they are comparing their algorithms and I hope they are good programmers for all the languages they tested otherwise the tests don't mean anything.
  • Taft12 - Thursday, November 3, 2011 - link

    I'm not surprised that part of the article would lead to programming language holy wars, but general benchmarks are utterly useless for Facebook. They should (and surely do) care only about performance of the compiled code and hardware platforms that run the site.
  • bji - Thursday, November 3, 2011 - link

    It's illogical to suggest that an interpreted language like Java or C# could ever approach C++ in speed when the same level of optimization is applied to each.

    In my experience, the least optimized C++ code can sometimes be approximated in performance by the best optimized Java code, depending on the task in question.

    Of course, once you spend time optimizing the C++ code then there is no way for Java to keep up.

    I have never used C# but I expect the result for it would be very similar to Java due to the similar mechanics of the language implementation.

    That being said, in many situations raw speed is not the most important factor, and Java and C# can have significant advantages in terms of mechanism of deployment, programmer productivity, etc, that can make those languages very much the best choice in some situations; which is why they are, in fact, used in those situations in which their advantages are best exploited and their weaknesses are least important.

    I think that Ruby takes the last paragraph even further; Ruby is so ungodly slow that it has to make up for it by allowing extreme productivity gains, and I expect that it must (I've never programmed in it to any significant extent), otherwise it wouldn't have any niche at all.
  • data003 - Thursday, November 3, 2011 - link

    While I've lurked this site for many years I just created an account to correct this erroneous bit of fail above.

    1. C# and Java are not interpreted languages. The are compiled at runtime into machine code.

    2. The C# JIT compiler can actually produce more efficient machine code than a compiled C++ binary.

    Since you have never used C# and clearly don't understand how it works, I'd suggest you refrain from commenting on it.
  • Jaybus - Friday, November 4, 2011 - link

    I agree that in some cases a JIT compiler can produce more efficient code, particularly when the application lends itself to runtime optimizations, however that is far from typical. Usually, for a single process, the JIT code, once compiled, will be reasonably close, though the static C/C++ code has the edge.

    But that is for the typical case. Facebook is not a typical case. Each web server is constantly starting many, many short-lived processes. Each process must start up its own copy of the code. This is where JIT fails badly to ahead-of-time compilation. It isn't the execution speed of the code after the JIT gets it compiled. The problem is the startup delay. Even with caching, the bytecode still must be compiled at least once for each new process, which in Facebook's case is millions of times. There is no such delay with ahead-of-time compilation. Therefore, Java and C# have no chance of competing in Facebook's environment.
  • erwinerwinerwin - Thursday, November 3, 2011 - link

    i wonder whether power consumption justifies them to create a new hardware w/ green power architecture and the cost they spend to having a custom build power supply running on 270volt, if it's only saves about 10-20 percent average of power consumption, rather than lets say make a corporate deal to the best power/performance servers producer on the market and modified it with water cooling (for example)???
  • Menetlaus - Thursday, November 3, 2011 - link

    Power savings absolutely justifies the work they did in customizing.

    20W less power consumption x 24/7/365 operation = 175KW.h (per server per year)
    175KW.h x $0.1/kw.h = $17.50 in power savings/year

    Just looking at the final image in the article there are easily 30 racks of 30 servers visable (30 x 30 x 17.50 =) $15 750/year in power saving.

    Since most power going into a computer ends up as wasted heat, if the 900 servers (from above) were consuming the additioanl 20W this would be ~18KW of additional heat being produced which needs to be cooled. This offers additional operational and capital cost savings due to the smaller cooling requirements.

    Water cooling may be a more efficient way of pulling heat out of the server rack, but the additional parts to move the water around the facility and to cool it adds to the total costs. Water is more efficient because it carries more heat/volume than air and with the piping the heat can be taken outside of the server room, while fans heat the air around the servers where another method of removing the heat is then required.

    The custom power supply at 270V and custom motherboard aren't really that difficult to get, as so many makers of each part already do custom designs for major PC makers (Dell/HP/etc). The difference between 208v and 270v from an electrical design standpoint isn't a big change, neither is removing parts from a motherboard.

    In short it's the economy of scale. You or I wouldn't be able to do this for a dozen personal systems as the costs would be huge per system, on the other hand for anyone managing 1'000's of servers the 20W/per adds up quick.

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