The short version is that the backups are a mix of short-term local backups + backups across the network on distributed filesystems + offline tape backup.
I can't speak to Drive, but the tape backup is certainly used for GMail. (There's a case study about Gmail having to restore from backup in the above link.)
https://landing.google.com/sre/sre-book/chapters/data-integr...
The short version is that the backups are a mix of short-term local backups + backups across the network on distributed filesystems + offline tape backup.
I can't speak to Drive, but the tape backup is certainly used for GMail. (There's a case study about Gmail having to restore from backup in the above link.)