Does this support delta/block-level sync for large files (e.g.: does mounting a 100 GB truecrypt container, modifying a file inside the container and unmounting it cause the entire 100 GB container to be uploaded)?
Does it utilize the native OS platform APIs for detecting file modification (e.g. inotify on linux) as opposed to scanning/polling large directories looking for modified date changes?
> Does this support delta/block-level sync for large files
Yes.
> Does it utilize the native OS platform APIs for detecting file modification
It uses polling.
Edit: inotify issue is here: https://github.com/calmh/syncthing/issues/9 (the author seems to want to implement this feature once go has a decent cross-platform file watching library)
Regarding detecting file modifications: my friend had issues with his synology diskstation eating 100% cpu with btsync with around 50k files. With less files it was down to 20%. We never debugged it properly but it may be polling issues, but it could also have been out of ram-swapping issues (512MB ram was not enough).
Others have reported issues with many files:
https://forum.bittorrent.com/topic/23802-syncing-600gb-10-mi...