The Google Dance

April 1, 2010 by  
Filed under Search Engine Optimisation, SEO
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What is the Google Dance and How often does it happen

The “Google Dance” is the period when Google rebuilds its rankings. During this time results fluctuate widely for a 3 to 5 day period.

The name “Google Dance” is used to describe the period of time when a major index update of the Google search engine is undertaken. These major Google index updates occur on average every 36 days or 10 times per year. During this time there are wild and often changing Search results as Google attempts to crawl and re-index literally billions of pages across the web. It can take up to 7 days to completely update the index.

Because Google customers depend on the search engine for reliable results 24 hours of the day, seven days a week, the timing of updates poses a serious issue. They can not shut down for maintenance and they cannot afford to go offline for even one minute. Hence, we had the Dance. Every search engine goes through it, some more or less often than Google. However, it is only because of Google’s reach that we pay attention to its rebuild more than that of any other engine.

How The Dance Has Changed

Since August 2003, the Google Dance is pratically no more. Or rather it has become less dramatic. Google now performs updates every week, with most movement occurring on Mondays. These ongoing updates feature mostly minor algorithm and index updates.

So, during any month there will be minor changes in rankings. This is because Google’s bot or spider is always running and finding new material. It also happens because the bot may have detected that a website no longer exists, and needs to be deleted from the index. During the Dance, the Google-bot will revisit every website, figure out how many sites link to it, and how many it links out to, and how valuable these links are. Because Google is constantly crawling and updated selected pages, their search results will vary slightly over the course of the month. However, it is only during the Google Dance that these results can swing wildly. You also need to consider that Google has multiple data centers, sharing more than 10,000 servers. Somehow, the updates to the index that occur during the month, and outside of the Google Dance have to get transferred throughout. It’s a constant process for Google, and every other search engine. These ongoing, incremental updates only affect parts of the index at any one time.
At any time during an index update you can check the Google servers, and they will display widely differing results, thus they are said to be “dancing”, and hence the name “Google Dance”.

In the past, the easiest way to check if the Google Dance was happening was to go to google.com, and do a search. Look at the blue bar at the top of the page. It would have the words “Results 1 – 10 of about 436,000. Search took 0.36 seconds” Then check the same search on www2.google.com, and www3.google.com. If you were seeing a different number of total pages for the same search, then the Google Dance was on. Once the numbers, and the order of results on all 10 servers are the same, you know the dance is over.

The Effect of the Dance

For most people, this event in itself is not important. However, for anyone in the search engine optimisation industry it used to be a period of note where pages got temporarily dropped for a whole a day. People panicked. Then they are re-added, and they are better placed than before, and everybody calms down again. It’s interesting to see the importance placed upon Google by so many people.

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