What's the Google dance? Well, it's really just a fun phrase for when Google updates its index. This occurs regularly, once a month, and can cause a lot of movement in rankings, meaning that it's come to be feared by many in the SEO industry and anticipated by others. The update isn't just one sudden switch, though, as each index update takes several days to complete. During this update the searches seem to ‘dance' between the old index and new index – that's the Google dance.

So why does it happen? Well, Google pulls its results from over ten thousand servers, and they can't all be updated at once – Google would have to go down for the update. Instead, each server is updated with the new index, one at a time. This can cause very strange behavior in the page rank process if two major sites located on separate servers happen to have a close linking bond. These sorts of separations are interesting and can contribute to a great deal of change and motion in page ranks. The most important thing to keep in mind is that eventually Google will get you into your proper place. Generally, if you behave, you will not be thrown down for long by the odd activity that can occur when Google is in the process of updating its index for your server (or for the servers of your favorite link partners.

One common misunderstanding is the idea that Google controls which server each kind of information is coming from, and so stores similar information on the same server. Google's index doesn't work this way – it's a big, disorganized mass of information that Google searches very quickly. This is a blessing in disguise because it allows your site to remain reachable via other sites that are related to it when the index is taking place. Your site generally won't suffer for too long when an update is taking place anyway, but if you are heavily dependent on Google results, you will see a slight drop for a short period of time. This drop is often followed by a slight spike especially if your page rank has increased since the last index.

The 10,000 servers that Google uses are distributed between seven datacenters all over the world. Google doesn't keep all of those eggs in one basket – they want to be able to lose one datacenter and have the rest survive. If part of Google goes down, people can still use the search engine and as I said before, this allows your site to be accessed via related sites if the server holding your sites index happens to go down. The datacenters that Google has put into play are enormous in comparison to most datacenters around the world. Google rivals some of the largest datacenters in the world with each of its datacenters and is probably the largest in the world if all were combined into one.

You see, the ‘time-to-live' for www.google.com is only five minutes – that means that Google's IP address can change every five minutes. This allows them to switch between their datacenters regularly, spreading the search load between them intelligently and routing around any damage. If you constantly entered the same datacenter with every search that you placed it would almost certainly fry within twenty four hours. Considering the number of users on Google each and every day, it is surprising that ten thousand servers is enough. A server can only handle so much traffic in a day and Google insures that it can hold more than any other service on the internet.

The datacenters updating their indexes at different times causes Google to do its dance. Unless you're looking for your website's ranking, you'd never notice this as your site is normally available at all times. The unfortunate bit is that often times you will lose your page ranking for a short period of time or your site will seem to have a lower number of pages indexed by Google. If you insure that you have several hundred pages available on Google at all times you will most likely be able to provide all of your content at all times either directly or indirectly.