Multiples Drive to Same Backup ID?

Here’s how I have things set up at the moment. I have two hard drives in my computer designated for my data. The first is my basic data drive, which contains all files except video. The second is my video drive, reserved for my ever-increasing video footage.

When I first set up Duplicacy, I installed a third, large drive as my local backup. Using the web GUI, I set up two backups, one for the data drive (D:) with the backup ID of COMPUTERID-Data and one for the video drive (E:) with the backup ID of COMPUTERID-Video. These are both stored on the backup drive (Y:). (This is then copied to Backblaze, although I don’t think that’s really relevant to my question.)

My video drive is nearing full capacity, so I’ve installed another for further video files (F:). Of course, I want to add this to my backup, but I’m unsure if I should create a new backup ID for F: or if I should add it to the existing COMPUTERID-Video. (Click the +, select F: for the directory, click the green icon next to “Backup ID,” and select an existing backup ID.)


  1. I may be moving files between drives E: and F:.
  2. I will eventually add additional drives for video. Alternatively, I may move all files from E: and F: to an expandable RAID or similar storage solution.

It seems like using one backup ID for all video is the right solution, since it may all be consolidated to one storage device eventually, anyway, but I confess I don’t totally understand how Duplicacy handles such things. Naturally, I want to avoid files being needlessly backed up twice when I move them. Advice is appreciated.

You should pretty much always use a unique backup ID for each repository - especially if they’re going to the same backup storage…

If you don’t, Duplicacy will see the contents as new each time and won’t be able to do proper incremental backups. You won’t lose de-duplication, but it will take a very long time to run the backup as it scans each file afresh - just like a backup run with -hash. Then, when backup B is complete and backup A (which has the same ID as B) runs, it’ll do the same rescan of your entire drive. You’ll have even-numbered revisions with metadata from one repository, and odd-numbered from another repo. That’s not good.

Incremental backups work by comparing the metadata - timestamp, pathnames, sizes etc. - of your last backup snapshot for that ID to the current repository. It’ll only backup files that have changed or been moved (and it’ll de-duplicate most of the moved chunks anyway), or been added. This saves time as only new or modified files are hashed, chunked, and committed to backup.

Use an ID like COMPUTERID-Video2 or COMPUTERID-Video_F or whatever. You’ll still benefit from de-duplication if you need to move files between the two locations.


Ah, thanks very much! Unique IDs it’ll be.

Also, is there any way to change an existing backup ID? Say, if I wanted to change COMPUTERID-Video to COMPUTERID-Video_E for consistency?

Honestly, the easiest way would be to just remove the backup ID and re-add it with the new ID.

Your first backup with the new ID will take longer - similar to a backup with the -hash option - but it’ll still de-duplicate most of the chunks and won’t have to re-upload everything.