Update detection and incremental updates


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Good morning,

I'm giving BT Sync a try as an alternative to Dropbox to sync some files between a Windows XP VM and my FreeBSD home storage server. Basic syncing works great, but I have one issue, and a couple questions.

One of the files I'm syncing is a semi-large (650MB) TrueCrypt volume. My normal work flow is to mount the volume, do some work on it's contents, and then unmount it. With Dropbox after unmount it would begin syncing immediately. With BT Sync, it appears to not detect that the file has changed. TrueCrypt appears to not be updating the Date Modified on the file. I used a Windows version of 'touch' to update the Modified time, and then BT Sync began syncing the file.

So I'm curious how Dropbox detected the file change without the modification date being changed, and if BT Sync could do whatever Dropbox is doing so I don't have to hack up a solution where the file gets touched after unmounting the volume.

My other question is does BT Sync perform incremental updates of files when they change between clients. I assumed so, since as I understand the BT protocol you'd compute new chunk hashes and then only have to transmit the changed chunks, but I thought I'd ask and get confirmation of that assumption.

Thanks in advance, and thanks for providing a FreeBSD client!

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So I'm curious how Dropbox detected the file change without the modification date being changed, and if BT Sync could do whatever Dropbox is doing so I don't have to hack up a solution where the file gets touched after unmounting the volume.

Sync is base on file timestamp. So if it not changed, Sync will not check the content of the file.

My other question is does BT Sync perform incremental updates of files when they change between clients. I assumed so, since as I understand the BT protocol you'd compute new chunk hashes and then only have to transmit the changed chunks, but I thought I'd ask and get confirmation of that assumption.

This is correct. Sync will transfered only changed chunks.

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