Sync actively monitors connected folders for changes at all times and will detect any changes to files or folders within about 10 seconds after the last change.
Different operating systems have limitations for folder-monitoring applications. For example, if a file is in a deeply nested folder on a Windows PC, it will not send change notifications for these deeper levels. To cover such cases, Sync periodically re-scans all folders for changes.
To make this re-scan as lightweight as possible, Sync only checks for file and folder modification time and size changes. If anything has changed, it re-hashes the whole file to find out which pieces of files have actually changed and need to be synced.
Sync rescans folder right after starting and periodically afterwards. The default rescan period is 600 seconds (10 minutes). You can adjust it by changing the folder_rescan_interval setting in Power user preferences of the Advanced preferences page.
If set to zero, Sync won't rescan folders at all, even upon restart. You might need it in the following cases:
- You've got really many files on your storage, so folder rescan time is comparable to the rescan period.
- You know that file changes are rare or never happen.
- Sync prevents your storage drive from entering power saving mode.