Ignore to proceed

[flashcard4290]

I am trying to sync two 10TB drives. One has about 2 TB free space and the other has about 3 TB free. Most of the files on each drive are also on the other drive. But there are some files on each drive that only exist on that drive and not the other.
When I set up a sync to get both drives to be exact copies of each other, just before proceeding there is a "Not enough space" to proceed. However there is a button to Ignore, which goes ahead with the sync.
I decided to go ahead and ignore and proceed. Can I expect the process to ignore the duplicate files that do not need to be copied and only copy the ones that do need copying?
Thanks,
James Harris

[xCSxXenon]

Of course, FFS always only copies "the ones that do need copying"
Telling it what it needs to compare and copy is what you do, as the user. If FFS threw that error, somewhere it calculated that there would be a space issue, but it's hard for anyone to say without further info. If there is >2TB of additional files between the two base locations you selected, you don't have enough space on one of them. I'm inclined to say that FFS is correct and you are likely to run into an issue, but all you've provided so far is a warning message and that you ignored it ¯\_(ツ)_/¯

Note that even identical files that are located in different relative locations are treated as different, FFS does not act as a duplicate finder