The Google explains:
“Our old index had several layers, some of which were refreshed at a faster rate than others; the main layer would update every couple of weeks. To refresh a layer of the old index, we would analyze the entire web, which meant there was a significant delay between when we found a page and made it available to you.
With Caffeine, we analyze the web in small portions and update our search index on a continuous basis, globally. As we find new pages, or new information on existing pages, we can add these straight to the index. That means you can find fresher information than ever before—no matter when or where it was published.”
Facts about Google Caffeine:
It processes hundreds of thousands of pages in parallel — if this were a pile of paper, it would grow three miles taller every second.
It takes up almost 100 million gigabytes of storage in one database and adds new information at a rate of hundreds of thousands of gigabytes per day — users would need 625,000 of the largest iPods to store that much information, and if those iPods were stacked end-to-end they would go for over 40 miles.