Google data centers - web ranking software

Check your web rankings in Google data centers
Read about Google dance

Google data centers - web position software

Semonitor can check your rankings in all Google data centers (60+) and Google test domains - www2 and www3.

Since January 2004 Google has closed its old data centers (,, etc.) and there are more than 60 new google data centers now that can be accessed by their ip addresses. Semonitor can check your web site rankings in all these data centers so you can predict your site's position on Google. You can find full list of currently working Google data centers on the corresponding tab after downloading Semonitor.

Below is information on Google data centers and Google dance.

Google danceGoogle dance overview

The name "Google Dance" has often been used to describe the index update of the Google search engine. Google's index update occurred on average once per month. During an index update there was significant movement in search results and Google showed new backward links for pages. However, in mid-2003 Google started to update it's index continuously. It appears that, still, there has to be an update of the complete index once in a while and during this time new backward links are shown. But, because of the continuous update, the effects on search results seem to be rather insignificant.

The Google search engine pulls its results from more than 10,000 servers. Naturally, an index update cannot be proceeded on all those servers at the same time. One server after the other has to be updated with the new index.

Many webmasters think that, during the Google Dance, Google is in some way able to control if a server with the new index or a server with an old index responds to a search query. But, since Google's index is inverse, this would be very complicated. As we will show below, there is no such control within the system.

Not only Google's index is spread over more than 10,000 servers, but also these servers are, as of now, placed in ten different data centers. These data centers are mainly located in the US (i.e. Santa Clara, California and Herndon, Virginia), indeed, in June 2002 Google's first European data center in Zurich, Switzerland went online. Other data centers in the US followed but the last one, which was opened in August 2003, appears to be located in Dublin, Ireland.

How data centers and Google Dance are related, is easily answered. During the Google Dance, the data centers do not receive the new index at the same time. In fact, the new index is transferred to one data center after the other. When a user queries Google during the Google Dance, he may get the results from a data center which still has the old index at one point im time and from a data center which has the new index a few minutes later. From the users perspective, the index update took place within some minutes. But of course, this procedure may reverse, so that Google switches seemingly between the old and the new index.

Google data centersIP Addresses and Domains of Google's Data Centers

The progression of a Google Dance could basically be watched by querying the IP addresses of Google's data centers. But queries on the IP addresses are normally redirected to However, Google has domains which resolve to the single data centers' IP addresses.

Those that keep an eye on Google's index updates often think that the Google Dance is over, when they see the new index at or when they don't see the old index at for some time. In fact, the update is not finished until all the domains listed above provide results from the new index.

The index updates at the single data centers seem to happen at one point in time. As soon as one data center shows results from the new index, it won't switch back to the old index. This happens most likely because the index is redundant at each data center and at first, only one part of the servers (eventually half of them) is updated. During this period, only the other half of the servers is active and provides search results. As soon as the update of the first half of servers is finished, they become active and provide search results while the other half receives the new index. Thus, from the user's perspective, the update of one data centers happens at one point in time.

Test DomainsThe Google Dance Test Domains www2 and www3

The beginning of a Google Dance can always be watched at the test domains and Those domains normally have stable DNS records which make the domains resolve to only one (often the same) IP address. Before the Google Dance begins, at least one of the test domains is assigned the IP address of the data center that receives the new index first.

Building up a completely new index once per month can cause quite some trouble. After all, Google has to spider some billion documents an then to process many TeraBytes of data. Therefore, testing the new index is inevitable. Of course, the folks at Google don't need the test domains themselves. Most certainly, they have many options to check a new index internally, but they do not have a lot of time to conduct the tests.

So, the reason for having www2 and www3 is rather to show the new index to webmasters which are interested in their upcoming rankings. Many of these webmasters discuss the new index at the Google forums out on the web. These discussions can be observed by Google employees. At that time, the general public cannot see the new index yet, because the DNS records for normally do not point to the IP address of the data center that is updated first when the update begins.

As soon as Google's test community of forums members does not find any severe malfunctions caused by the new index, Google's DNS records are ready to make resolve the data center that is updated first. This is the time when the Google Dance begins. But if severe malfunctions become obvious during this test phase, there is still the possibility to cancel the update at the other data centers. The domain would not resolve to the data center which has the flawed index and the general public could not take any notice about it. In this case, the index could be rebuilt or the web could be spidered again.

So, the search results which are to be seen on and will always appear on later on, as long as there is a regular index update. However, there may be minor fluctuations. On the one hand, the index at one data center never absolutely equals the index at another data center. We can easily check this by watching the number of results for the same query at the data center domains listed above, which often differ from each other. On the other hand, it is often assumed that the iterative PageRank calculation is not finished yet, when the Google Dance begins so that preliminary values exert influence on rankings at that point in time.

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