Storing backups
How are the backup files stored? Is it efficient and secure?
When assessing the storage approach of each tool, we want to know if it’s efficient and secure. Efficiency comes from avoiding duplication of file storage to save storage space and file transfer times. If the algorithm is smart, it’ll avoid backing up files that haven’t been changed. File compression is also a factor here. Encryption ensures security of your files.
Grsync stores the files themselves and they can be accessed in a normal manner. So, they’re not encrypted but there is an option for compression, although support is basic. Subsequent backups take up less space because it checks to see if the files have changed before backing them up again, but there’s no concept of snapshotting and being able to restore previous versions of files.
Because Deja Dup uses Duplicity as its backend, it’s not capable of keeping the backed-up files in an easily accessible form. If something went wrong with Deja Dup, the official advice is to work with Duplicity to carry out a manual restoration. The files are stored using GPG encryption. Thanks to the Duplicity backend, the backup files are incremental, and backing up repeatedly only stores the areas of files that have altered since the last backup.
BackupPC stores its backups as reverse deltas. This means that the most recent backup contains all of the information needed to reconstitute a backup. This isn’t the case for Duplicity (which powers Deja Dup), meaning that if one incremental backup is lost then only the backups leading up to that loss can be reconstituted.
Through a process called ‘deduplication’, BackupPC and Vorta can recognise if identical files (or even chunks of files) are present in more than one backup, even from more than one system, and they save time and storage space by only storing that data once. Worth considering if you back up more than one system.
Back In Time stores every file that is backed up for every snapshot. However, it uses hard links for files that have not changed so the unchanged files don’t take up any disk space.