Google dance - The index update of google
Skill Level: Novice
Article by: eFactory

IP 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 www.google.com. However, Google has domains which resolve to the single data centers' IP addresses. These domains as well as their IP addresses are shown in the following list.

Domain IP Address
www-ex.google.com 216.239.33.100
www-sj.google.com 216.239.35.100
www-va.google.com 216.239.37.100
www-dc.google.com 216.239.39.100
www-ab.google.com 216.239.51.100
www-in.google.com 216.239.53.100
www-zu.google.com 216.239.55.100
www-cw.google.com 216.239.57.100

For every domain www-xx.google.com, there is an additional domain www-xx2.google.com. The IP address of such a domain ends on .101 instead of .100. These pairs of domains and IP addresses belong to the same data center and, hence, the same index is searched by queries on them.

Note: Searches at www-sj and www-zu are currently redirected to other data centers. Since results for searches at their IP addresses fluctuate heavily during a Google Dance, also these searches seem to be internally routed to other data centers. As we can see from our statistics for Google's DNS records, there are currently no searches at www.google.com directed to www-sj or www-zu. So, we can assume that the two data centers are offline.

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 www.google.com or when they don't see the old index at www.google.com 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.

Finally, it shall be noted that the access to the single data centers is generally controlled by the DNS only, but sometimes queries are redirected. However, this is easy to detect: When for a query at one of the domains listed above, the links to Google's cache do not comply with the IP address that belongs to the domain, then the query is redirected. If this happens, Google inhibits - for whatever reason - the access to one data center.

Contents

• The Technical Background of the Google Dance
• Google Dance and DNS
• IP Addresses and Domains of Google's Data Centers
• The Google Dance Test Domains www2 and www3
• The New PageRank Values during the Google Dance

++ Back to top ++