Originally Posted by Xuoxo
What is a Google dance?
The name "Google Dance" is often used to describe the index update of Google search engine. Google's index update occurs on average once a month. Can be identified by significant movement in search results and, especially Google's cache of all indexed pages reflecting the status of Google last crawl. However, the update does not proceed as an index switch to another at a point in time. In fact, it takes several days to complete the update of the index. During this period, the old and the new index alternate on. In a first stage, the results of the new index occur sporadically. But later, appear more frequently. Google dances.
Expertise in Google
The Google search engine pulls its results from more than 10. 000 servers that are simple Linux PCs are used by Google for reasons of cost. Naturally, an index update can not be processed on all servers at the same time. A server after the other has to be updated with the new index.
Many webmasters believe that during the Google Dance, Google is somehow able to control whether a new index server 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 discussed below, no such control in the system. In fact, the reason for the Google Dance is Google's way of using the Domain Name System (DNS).
Google Dance and DNS
Not only does Google index spans more than 10,000 servers, but these servers are, for now, placed in eight different data centers. These data centers are mainly in the U.S. (Ie, Santa Clara, California and Herndon, Virginia), in fact, in early June 2002 Google European data center in Zurich, Switzerland went online. It is very likely that more data centers to come, which may be spread across the world. However, in January and April 2003, Google has made two data centers in the stream is back in the U.S..
In order to drive traffic to all these data centers, Google thoeretically could record all queries centrally and then send the data centers. But this would obviously be ineffective. In fact, each data center has its own IP address (numerical address on the Internet) and how these IP addresses accessed is managed by the Domain Name System.
Basically, the DNS works like this: On the Internet, data transfers always take place in between the IP addresses. The information about which domain resolves to the IP address is provided by DNS name servers. When a user enters a domain in your browser, a name server configured at the local level it takes the IP address of that domain by contacting the name server that is responsible for that domain. (The DNS is structured hierarchically. That illustrates the process would go beyond the scope of this article.) IP address is cached in the server names, so you do not need to contact the responsible name server each Once you create a connection to a domain.
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