Windows 8.1 and OneDrive changes

Windows 8.1 introduced significant changes in how OneDrive (previously known as SkyDrive) works, and one of these is the possible replacement of actual files in any dedicated OneDrive folder with placeholders, which MS calls Smart Files.

These placeholders deliberately mimic real files (they have the same properties) so that if you have a profile that scans such a OneDrive folder, it may now think files are there (and maybe changed since 'last time' or 'now out of date' - depending what it is comparing them with) and try to copy or update them, leading to errors (because the real files are not really there). You may need to open Windows File Explorer, right-click on "OneDrive" in the left-hand pane, and click "Make available offline" to remedy this.

Note that descriptions of this new OneDrive behavior in Windows 8.1 vary (for example, between the official MS line and various reviewers/testers) and the new functionality may react in unexpected ways. 'Your mileage may vary'.

It should also be pointed out that it is not necessarily a good idea to have two 'synchronization' (two-way file traffic) processes affecting the same location(s), given that one process may believe changes effected by the other are the result of human choice/interaction. Hence, using SyncBack to synchronize some other repository with a OneDrive folder that is itself being synchronized (by Windows) with the 'cloud' side of OneDrive could conceivably introduce feedback and/or 'race' conditions.

SyncBack V7, and newer, will ignore placeholder files.

For Windows 10 users, refer to Windows 10 and OneDrive Files On-Demand articles.