No, not global. Each office only really need access to their own documents, there are over 2,000 offices though. It does need to be high speed and yes cost is a factor.
If you are willing to try out some beta software, give https://didgets.com/ a look. You can load in hundreds of millions of documents or other kinds of files and put meta-data tags on each of them. Queries for individual documents or sets of them execute with sub-second speeds. The software is in beta and available for free download.
Currently working on the indexing feature to index the contents of the files too.
