I am looking for a backup software (FOSS, running on Linux) which is able to back up about 1 TiB of data in mostly big files (smallest around 3 MiB, largest around 4 GiB) to a hard disk drive.
The clou is: On the backup hard disk drive, there needs to be at least one working copy of the data at any point in time. However, I do not want to store two full (!) copies of the data, not even temporarily. Therefore, let’s assume I only have 1.5 TiB capacity on my backup hard disk.
In order for the backup software to figure out which files were just saved twice and delete the old copy, it needs to operate on file level (sub-file level is not required). However, incremental backups are not necessary — I always do full backups. The motivation behind always doing full backups is to eliminate the possibility of bitrot and detect hard disk drive failures early by keeping them busy and rewriting every sector once in a while.
Which backup software fulfills my requirements? I looked at rsnapshot, bacula, duplicity, obnam and bup. To the best of my knowledge, none of them fulfills this requirement.