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Everyone seems to agree that Google assigns a viewable page rank to a
website or page every 80-120 days. Depending on when you
publish your page, this means you may have to wait anywhere from 1 to
120 days to find out what its page rank is. What is much
debated though is how often Google actually recalculates page
rank. For some reason lots of people are under the impression
that at any any given time Google knows your exact current page
rank. But if you look at the data you will understand that
real time page rank is not possible. There are countless
reasons why it can never be real time or even achieved with only
marginal latency.
First lets assume there is no latency between Goggle's data centers,
and they have arrays that can crunch the numbers in a few
seconds/minutes. Now you publish a page at
1.com/a.htm. Google sees the new page and domain and gives
you a 0PR. 5 minutes later 2.com/b.htm which carries a PR5
backlinks to your site. How long before Google sees the
backlink and correctly updates your PR? To further complicate
the issue what if 2.com/b.htm picks up 10000 relevant backlinks and
jumps to PR6? The pagerank formula is too dynamic to afford
real time page rank assignment. Snapshots are required which
would make the data static before the formula can be run.
Second look modern hardware limitations. Even if every data
center was running arrays of IBM Blue Gene super computers writting to
U640s drives there would be too much information and resource demand
for real time page rank. While Google maybe able to index
sites in only a few minutes this is achieved over a massive array of
servers scattered across the globe. The simple fact there are
30,000,000,000+ web pages and only so many FLOPS of processing power
available shows that a PR update requires anywhere from several hours
to weeks.
If you watch the PR updates closely you will see changes happening over
several weeks. Backlink updates, page ranks resetting, data
centers showing different results. To say that Google is
capable of real time updates is saying that the whole two week deal
with back links, data center variations, and so on are just smoke and
mirrors. Running an array at load vs idle is a huge monetary
difference. No corporation is going to do it for the sake of
smoke and mirrors.
All of this is not saying that Google does not do some of this to limit
analysis of the algorithm. If Google could do real time page
rank updates I doubt they would as many others have said. It
would lead to abuse and make the system too predictable. In
short just because you can does not mean you should. But
based on current technology and architecture real time page rank
updates are not possible.
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