Brian from Backblaze here. Yep, we checksum the file on the client before sending it. In practice for any one user the number of "silent bit flips" on disk is

Brian from Backblaze here. Yep, we checksum the file on the client before sending it. In practice for any one user the number of "silent bit flips" on disk is very low and you probably wouldn't notice it (maybe 1 note in your mp3 file is slightly off). But when we check the checksums every few weeks we absolutely see it occur in our datacenter at our scale probably every day and take steps to heal the files (either from other copies we have or ask the client running on the customer's laptop to retransmit the file).