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I want to maintain a large file synced between my android device and a PC. I will be doing small changes to this file file all the time on the device, and I want these changes to be reflected on the PC. Ideally the file should not be uploaded in full everytime it changes (because it is so big), but only the differential changes (which are small). Is there a tool / app that does this? Does Dropbox / Dropsync work like this?

Update: This says that Dropbox only uploads the differential part. But I do not know if the same applies to Dropsync.

  • @beeshyams Before I consider rsync (which I suppose will take more config to do), I would like to know if Dropbox for Android has differential sync, at least for some file types? I am thinking of PDFs, and the kind of change I make on the tablet that should get synced is annotations. – becko Jul 22 '17 at 14:22
  • Let us continue this discussion in chat. – beeshyams Jul 22 '17 at 17:12
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Differential sync or Delta sync is a feature that is available only on the PC version and not on Android as explained in Dropbox help pages Delta sync for Android

Power:....Delta sync means you have to carry out hashing operations on the file, which on pretty much all mobile devices is a non-power optimised operation....

Hashing Overheads for small files: Now, if the file is very large, and the change set is very small, sure there will be a tipping point, but for mobile stuff we aren't talking about a usage pattern which generally covers files hundreds of MB upward in size being edited, its going to be brand new files (photos, videos etc) or small changes to documents etc....You aren't going to be editing huge videos on an Android phone or tablets for example.

(Emphasis Supplied)

  • If Dropbox for Android doesn't do Delta Sync, Dropsync logically cannot do, since it feeds Dropbox. Besides, app forum talks of comparing files but not differential or Delta sync

  • I couldn't find any alternative cloud solutions that implement this sync on Android, perhaps for the reason mentioned earlier. Even services like Own Cloud which have an Android app, give similar reasons

  • Only alternative I can think of is using rsync which does incremental backups, which is faster than differential backup (See a nice tabulated summary here)

    Some pointers that may help you implement this solution ( should you decide on this route, it may help to ask a separate question for details )

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    Thanks for a very thorough answer. I will consider rsync, and post another question if needed. – becko Jul 22 '17 at 16:54
  • Xodo PDF reader claims to have this feature (for PDFs only): "For Dropbox, data use is minimized by uploading only the changes you make, not the whole document". play.google.com/store/apps/…. I am testing it myself, anyone has experience with this? – becko Jul 28 '17 at 8:03
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    Giving that this feature seems to exist for PDFs, I am setting up a dedicated thread for this format only, here: android.stackexchange.com/q/180263/6813. – becko Jul 28 '17 at 8:18

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