Remote Backup Between Two PR4100s Copy/Synchronize?

I have two PR4100s on the same network and want to use one to back up the other.

When setting up this up, I have the choice of Copy or Synchronize.

If I use Copy, does that mean it copies every single file every time I run the job?

If I use Synchronize, does that mean it copies only new or changed files and deletes/renames as needed?

HI WDTraveler,

During the Remote Backup job, “Copy” will copy all the files of source My Cloud to destination My Cloud device but “Sync” will copy the new or updated files, also deletes the file if deleted from the source My Cloud. For further details, you can have a look on below KBA:

https://support.wdc.com/knowledgebase/answer.aspx?ID=11807#stepc1