[tlipcon]

Colossus metadata is stored in Bigtable: see https://cloud.google.com/blog/products/storage-data-transfer...

Spanner stores its data in Colossus, so there would be some bootstrapping issues to resolve to move it to Spanner over Bigtable. (Bigtable also has the bootstrap issues but has solved them already and there are additional difficulties due to some details that I probably am not at liberty to share)

Spanner is used for metadata for many other very very large storage systems, though.

[packetslave]

Yeah, that was my understanding as well. Colossus stores metadata in Bigtable on top of a smaller Colossus, which stores its metadata in Bigtable on top of an even smaller Colossus, which… [insert more stacks of turtles here] ends up in Chubby.

Public presentation here: http://www.pdsw.org/pdsw-discs17/slides/PDSW-DISCS-Google-Ke...