Limits of FreeFileSync

[cweber50]

FreeFileSync works excellently on my system, with an incredible speed (as I save everything twice for RAID-1-like safety, it has to analyse metadata of 400'000 files. It can do that in less than 2 minutes).
This speed, however, suggests that FreeFileSync works with parallel threads and reads all metadata into memory before comparing data.
If this is so: is there a limit (defined by memory size) to the number of files FreeFileSync can handle?
If so, then this limit should be described in the documentation.

[Zenju]

I made such calculations about 2 years ago, but the data structures have not changed (much), so this should still be valid:

FFS can synchronize about 1.7 million file pairs (= existing on source and target side) for each 1 GB RAM available.

I can hardly remember feedback from users having too little RAM for sync, so in general this is not something users should be concerned about.

[Zenju]

This info was added to the FAQ.