Weirdness When Files Already Exist On Both Sides

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I have a hard time understanding what BtSync is trying to do right now with my files. I did a stupid thing and tried to sync a folder containing a little under 300G of data... Anywho.


Let's set the playground here.


A is a server I own. It contains all the files I need, because I use it as a backup drive. It is running debian.

B is my own computer. It is running windows 8.1. The hard drive where data are stored is in ExFat.


Usually what I do is just using FileZilla to transfer files one way or another. It's a bit of a pain, and I was going to try another software when a friend of mine talked to me about BtSync. Which, to be fare, kind of look like it could do pretty much what I need.


Back to my issue. In this folder, A, I'm trying to sync, I have a set of file that I already synced (using FileZilla) and a bunch of new files, I did not transfer yet. Let's call the first one F and the second one G.


So F is already on A and B. And in this particular case, I want to add G to B.

Here is what I did:

1/ Download/install BtSync on A (Debian), add the folder that contains all files of F and G.

2/ Wait for the indexing to be over (which took quite a long time)

3/ On A, share said folder, read and write

4/ Install BtSync on B (Win 8.1), and add the shared folder, setting the destination to the folder already containing all files of F


What I expected to happen:

After the indexing on B, I expected BtSync to just skip all files in F (an exact copy of F on A) and transfer all files in G from A to B


What actually happened:

Actually I have no idea...

I have transfers going from A to B, but also from B to A (again, anything in B was already on A).

What the heck is happening? Is BtSync trying to upload everything both way to finally understand all files are exactly the same? Isn't the indexing part supposed to avoid this stupid process?


I would really like to understand the issue here, and possibly avoid it. Is it something to do with access rights on the files? The fact that windows is non case-sensitive? It should not be difficult to see that all these files are exactly the same.


I would have shut down BtSync if I was not half sure that most of my files on both computers where in the middle of a transfer, hence corrupted. So right now I'm just waiting to apparently transfer 300G both ways.


If you have any help on this one, I would greatly appreciate it!


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The use case it pretty much valid. In your case Sync should compare and make sure that F set of files already present on your B computer and then sync only G set of files. First of all - It is very unlikely that Sync "corrupt" your files - if files are not huge, Sync usually delivers them to a temp file with !sync extension and only when transfer complete - replaces the original file with !sync.


Second - are you sure that transfer actually occurs? When Sync merges file trees, it may show a very rapid file transfer, though no transfer actually occurs.


Third, your folder on A and B must have completely same folder structure and files positions. Otherwise (even 1 level folder difference) it will make a duplicate of everything.


Fourth, could you please check if the FTP client and server you use do not change mtime of files? I.e. that the mtime you have on Debian is the same you got on Win8?

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