Backup and restore

An approach that I'm using:

- for DB: just a full dump every night, placed/copied into daily (up to 30 days), weekly (up to a year), and monthly (no limit). The dumps are gzipped, encrypted using openssl with public/private keys (x509), then uploaded to Amazon S3. Those folders on S3 (daily, weekly, monthly) have respective expiration policies.

- for moodledata: I only focus on "filedir". I've tested locally with duplicity and it works fine (with monthly as full back up and daily as incremental (the daily difference are stored in a tar ball). I'm looking into using duply to ingrate S3 into the backups process.

However, our site is small so the above works fine for us, but I think it should scale for your setup.  Bandwidth could be a problem if you do too many full backups as duplicity doesn't have synthetic full backups, but you don't seem to have bandwidth cost. The number of full backups will depend on how big your storage and how likely is corruption (corruption to any full or incremental backup will affect the whole chain down to the next full).