Bigtable, and presumably Spanner, goes beyond that. Data chunks have checksums and they're immediately re-read and verified after compactions, because it turns

Bigtable, and presumably Spanner, goes beyond that. Data chunks have checksums and they're immediately re-read and verified after compactions, because it turns out that errors do happen and corruption also happens, even when you use ECC — roughly once every 5PB compacted, per Jeff Dean figures.