I'm sorry, but 7 petabytes for the largest search index in the world? I'm hoping the reporter misquoted the developers here. If we conservatively assume servers with half a terabyte of hard disk space, that's 14,000 servers for the web index. Google was estimated to have 450,000 servers in 2006, and presumably has many more than that now. So less than 5% of their server stack would be required to store that size of web index. Considering that web search is still Google's core product, this seams easy to believe. And much more if you include image caching, maps, videos....