Google的cluster 到底有多大？

http://www.tnl.net/blog/entry/How_many_Google_machines

有人根据Google的IPO上市报告中的一些信息， reverse engineer出google的cluster到底有多大

http://www.computer.org/micro/mi2003/m2022.pdf

How many Google machines
April 30, 2004
An interesting tidbit coming out of the Google S-1 filing is that they have spent about $250 million on hardware equipment. From there, we can get a few guesses at the magnitude of the Google system. Based on quick back of the envelope calculations, it looks like Google is managing between 45,000 and 80,000 servers. Here's how I arrived at this conclusion:

According to calculations by the IEE, in a paper about the Google cluster, a rack with 88 dual-CPU machines used to cost about $278,000. If you divide the $250 million figure from the S-1 filing by $278,000, you end up with a bit over 899 racks. Assuming that each rack holds 88 machines, you end up with 79,000 machines.

However, one must recognize that equipment is not all CPUs. As a result, you must discount the figure of $250 million to account for routers, firewalls, machines for employees, etc... So let's assume for a minute that only about $200 million is going to the CPUs. That still leaves us with 719 racks or a bit over 63,000 machines.

Even if we discount other equipment to be costing $100 million, we end up with a bit over 47,000 machines on 539 racks.

So how much processing power is that? Well, once again, the Google cluster document provides some interesting tidbits. Per the document, the racks that were used were
88 dual-CPU 2Ghz Intel Xeon servers with 2 Gbytes of RAM and an 80-Gbyte hard disk.

That means that, on the low end, the Google cluster has the following stats:
539 racks
47,432 machines
94,864 CPUs
189,728 Ghz of processing power
94,864 Gb of RAM
3,705 Tb of Hard Drive space

In the middle range of my estimates, the cluster would have:
719 racks
63,262 machines
126,544 CPUs
253,088 Ghz of processing power
126,544 Gb of RAM
4,943 Tb of Hard Drive space

And on the high end of my estimates:
899 racks
79,112 machines
158,224 CPUs
316,448 Ghz of processing power
158,224 Gb of RAM
6,180 Tb of Hard Drive space


Assuming that the 1Ghz chip is going at about a third the gigaflops of a 2Ghz processor (3.3Gflops), we can then guess at the size of the Google supercomputer. Just for the sake of argument, let's go with 1 Gigaflop per processor. This means that the Google supercomputer has about 189 teraflops of power on the low end of my estimates, 253 teraflops on the middle end, and 316 teraflops on the high end. This would easily put it on top of the list of fastest computers in the world.

Any way you slice it, that's a lot of power.