[IDEA]Add the “differential” backup mode.

[LrbsX]

Just describe your idea

My server's archive size is quite large, which results in the usage of this plugin causing just three backups to consume 40GB of space. Therefore, I would like to request the addition of an differential backup mode to save on the space occupied by backup files. Specifically, this backup mode would operate as follows:


1. When the plugin is run for the first time on the server, it performs a full backup.
2. According to the pre-set backup schedule, during the next backup, it compares the current server archive with the initial full backup taken when the plugin was first run and backs up only the files that have changed or been added.
3. Repeat step 2, still comparing with the initial full backup and backing up only the differing files.
4. Until after a certain backup, it detects that the size of the current differential backup has exceeded X percent (X being a configurable percentage, set to 0 to disable the check) of the initial full backup; or it detects that it has been N minutes since the last full backup (N being a configurable timeframe, set to 0 to disable the check); or it detects that M number of differential backups (M being a configurable count, set to 0 to disable the check) have been made since the last full backup, then the next backup will again be a full backup (any one of these three conditions can trigger this action), and subsequent comparisons will be based on this full backup.
5. An addition to the behavior of the existing "maximum number of backups to retain" option: most of the time, it will only clear differential backups and not full backups, unless all differential backups dependent on a particular full backup have been deleted over time, in which case that full backup can also be cleared.

In this way, users will only need to overwrite the dependent full backup with a differential backup to complete the backup recovery operation.

[DVDishka]

It is very interesting idea. I am thinking about something like that for a long time period. I think I will implement this feature after some storage protocol implementatins like Google Drive and S3. Thank you for your idea!