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Forum Discussion
Dropbox uploads TOO fast
Hi All,
This may sound like a strange glitch. But, I use dropbox to send important files to paying clients, so I want to try to figure out what is going on to make sure that I don't send people...
- If you add a file to your Dropbox file, which is identical to another file on your account, then the Dropbox desktop application recognizes they are the same, so it creates a duplicate of the original file on the site and instantly 'syncs' the file.
This works even if the new file has a different name. I've tested on on my device with a 1 GB video.
Moved it into the Dropbox folder from a different location on my hard drive, outside of Dropbox.
The corrupted file was added through the Dropbox folder on my desktop
The corrupted file was added through the Dropbox folder on my desktop
Jay
Dropbox Staff
Dropbox StaffIf you add a file to your Dropbox file, which is identical to another file on your account, then the Dropbox desktop application recognizes they are the same, so it creates a duplicate of the original file on the site and instantly 'syncs' the file.
This works even if the new file has a different name. I've tested on on my device with a 1 GB video.
This works even if the new file has a different name. I've tested on on my device with a 1 GB video.
I didn't know that. Super useful. Thanks!
I have noticed something similar with audio files. I will upload 20GB of audio files which takes a while. I then make a tiny change to the audio in those audio files.
This audio is a bunch of 30 minute wave files of a tv program split into its various components, dialogue, music, effects, full mix etc. I change one tiny 5 second segment. That is the only thing that has changed.
I erase the old files in DB, I recreate the files, give them different names and they have different timestamps. They are almost identical to the old files as far as content goes except for the changed 5 secs of audio across all the wave files, the names and the time stamps.
DB seems to upload these very very quickly. Is DB so clever that it compares the content of the new and old files and updates the original uploaded files only altering the changed 5 secs in the whole file, plus the name and the time stamp?
- Rich
Super User II
KMT333 wrote:
Is DB so clever that it compares the content of the new and old files and updates the original uploaded files only altering the changed 5 secs in the whole file, plus the name and the time stamp?
Yes. Before every file is uploaded, it's split into 4MB chunks and then hashed. Before uploading the chunks, Dropbox compares the hash of each chunk to the hashes of all the chunks in your account. If there's a match, Dropbox doesn't upload that chunk. It already exists online, so no need to upload it.
Now the next part is dependent on the applications writing your files. If, when a file is modified, an application rewrites the entire file or just writes data to the beginning of the file, it's likely that every chunk of that file (and every hash) will be different, resulting in Dropbox having to re-upload the entire file. But if the application only rewrites a portion of the file, or just adds new data to the end of the file, the majority of your file remains the same, so most of the hashes remain the same, and Dropbox only needs to upload the chunks that have changed. In such a case, it will appear as though Dropbox has re-uploaded the entire 20GB file when in reality it's only uploading a few 4MB chunks.
