TL;DR: If you are using Dropbox as a sole backup of your files, think again. Without making a mistake, you might lose your files.

I started using Dropbox back in 2009 and have always loved the service. Over time, I kept moving more and more files to my Dropbox folder and eventually had to upgrade to the Pro plan to keep up with the space requirements. In particular, I moved there all of my photos in order to be able to view/share them on-line and also to have them backed up. In April of this year, a hard drive in my laptop was running low on space so I decided to use the Dropbox’s Selective Sync feature to unsync some large directories from the laptop. Because there was never any problem with the service and also because it’s already the year 2014, I thought it might be about time that one can trust a cloud-based storage service and use them as a sole backup of their files. Boy, I was wrong.

On 29th April 2014, I opened the Selective Sync dialog, unchecked directories called 2003, 2004, …, 2014 from the Photos folder (and few other directories) and clicked the ‘Update’ button. After that, the Dropbox client froze and didn't show any sign of life for a couple of minutes, so I decided to kill it and restart it again. These directories are large and they might be too big of a bite for Dropbox, I thought, and unsynced them one by one instead. Everything worked well, the directories disappeared from the local hard drive, but they were still available on Dropbox’s website. All good.

About two months later when I was preparing for a defence of my PhD thesis, I was looking for an old presentation but couldn't find it. The directory was there but it was empty. I would have never deleted these files, something must have gone wrong. I contacted Dropbox support which then broke the news to me: there was a delete event of 8343 files from 2014-04-29 at 14:57:30 GMT (UTC). Looking at the log record from this event, I realised most of the missing files were my photos! All the directories were still in place but many of them were empty, as if Dropbox randomly deleted some files and left some others intact. I was devastated. All those memories and the effort with collecting and organizing the photos…. gone.

From all this information it seems that Dropbox client first deletes files locally before it informs the server about the new selective sync settings. Consequently, if the client crashes or is killed before the server is contacted, the files remain deleted without any trace. After the client restarts again, it only sees there are some files missing and syncs this new state with the server. Unfortunately for me, Dropbox only keeps a copy of deleted files for 30 days (unless you pay $40/year for some Packrat feature) and I found out about this event after two months.

For me it’s most likely over, there is nothing I can do now, maybe try to get some photos back from my friends who went to same trips. Anyway, I decided to share this story publicly for three reasons:

A bit of publicity might convince Dropbox to put some extra effort and maybe find a way to restore my files. To let other Dropbox users know about this issue so that this doesn't happen to them. Basically after doing any major changes in Dropbox settings, one should check the Events page on Dropbox website to make sure no files got deleted. Dropbox team can use information from this story to fix the problem. Here are few suggestions what can be done:

a) Make the application of the selective sync settings transactional, either is succeeds completely or fails gracefully.

b) Enable the Packrat feature by default for every paying customer, without any extra cost. Looking at the storage plan pricing for Google Drive, there surely is a space for you to do that. Or, at least, keep the delete history as long as the deleted files fit into user’s quota, it’s a space users already paid for.

c) Use machine learning to detect a strange activity on user accounts and notify users by email if it happens. For example, most of my activity over the years consists of adding large number of new files and changing/deleting a small number files from time to time. A sudden deletion of 8343 files is surely a strange activity in this context.

Many thanks for reading and up-voting this story on Hacker News.

PS: At least I defended my PhD thesis even without that lost presentation, but the photos are gone nonetheless.

PPS: For the sake of completeness, I'm attaching a complete record of my communication with the Dropbox support, see below.

EDIT (on 2014-07-30): Many thanks for all the feedback. Yesterday night I got an email from Dropbox saying that they worked with their engineering team and were able to restore 1463 files. Also I received some credit for my future use of the service. Better than nothing.

Follow me on Twitter at @jancurn