And they reveal exactly zero details. I know a bit about it, but not enough to say exactly what semantics it offers to file system clients. I believe it is not POSIX-like, hence the need to layer Spanner and GCS over it.
There's been a teensy bit more details than that, e.g. [1]. If you think about exactly the file semantics that Bigtable would require (append, pread) that's exactly what is provided. Note that Colossus and D are two separate things. Google systems can use D without Colossus and a long time ago people used Colossus without D, although today Colossus/D is implied. The presentation gives the broad strokes of how Colossus is able to bootstrap itself from Chubby. It helps if you've also read the Bigtable paper [2].
??? The original GFS paper, which the chat references repeatedly, was clear about the semantics not being POSIX-like. The interview mentions that, too, along with stuff like snapshots. Colossus is basically the same, with increased scalability.
