I can give you my example -- I have an open source backup tool called Snebu which uses an sqlite DB to store the backup catalog (file names, file hash, metadata

I can give you my example -- I have an open source backup tool called Snebu which uses an sqlite DB to store the backup catalog (file names, file hash, metadata etc), whereas the individual files are stored in a vault area (currently just a disk volume, with files named after the sha1 hash). Backup data is sent to it by piping in tar format to the main process, which updates the catalog DB and deposits files into the storage vault. I'd like to add cloud capabilities, but for that I'd have to run the backend process somewhere that can easily update the DB, and easily read/write the data in the vault, along with syncing the full DB to the vault location after a backup. My other option is to run everything locally, and compute a delta file between versions of the DB and send that delta over to the vault (i.e., do D2D2C backups). Edit: Another possible requirement -- I'd like to pack multiple smaller files into an archive file, and deposit that into a bucket. But as files age out of the archive, I'd like to be able to move active ones out of it and into a new one. Right now, I'd have to re-create the still-valid backup data out of on-hand information, upload the new archive, then send a command to delete the old one.