The key thing to understand about GFS and relatives is how essential it is for distributed computation.

It is natural for us to look at a big file and think, "I need to do something complicated, so I'll do a distributed calculation, then get a new file." This makes the file you start with, and the file you wind up with, both bottlenecks to the calculation.

Instead you really want to have data distributed across machines. Now do a distributed map-reduce calculations, and get another distributed dataset. Then create a pipeline of such calculations. Leading to a distributed calculation with no bottlenecks. Anywhere.

(Of course this is a low-level view of how it works. We may want to build that pipeline automatically off of, say, a SQL statement. To get a distributed query against a datastore.)

Absolutely essential for this is the ability to have a distributed, replicated, filesystem. This is what GFS was. When you try to scale a system, you focus on your current bottlenecks, and accept that there will be later ones. GFS did not distribute metadata. It did not play well with later systems created for managing distributed machines. But it was an important step towards a distributed world. And the fact that Google was so far ahead of everyone else on this was a giant piece of their secret sauce.

True story. I went to Google at about the same time that eBay shut down their first datacenter. So I was reading an article from eBay about how more work it took to shut down a datacenter without disrupting operations. And how proud they are at succeeding. And then I saw the best practices that Google was using so that users wouldn't notice if a random datacenter went offline without warning. Which was a capacity that Google regularly tested. Because if you're afraid to test your emergency systems, they probably don't work.

What eBay was proud of doing with a lot of work, was entirely taken for granted and automated at Google.