The issue with a client app backing up dropbox and onedrive folders on your computer is the files on demand feature, you could sync a 1tb onedrive to your 250gb laptop but it's OK because of smart/selective sync aka files on demand. Then backblaze backup tries to back the folder up and requests a download of every single file and now you have zero bytes free, still no backup and a sick laptop. You could oauth the backblaze app to access onedrive directly, but if you want to back your onedrive up you need a different product IMO.
That would make sense for online-only files, but I have my Dropbox folder set to synchronize everything to my PC, and Backblaze still started skipping over it a few months ago. I reached out to support and they confirmed that they are just entirely skipping Dropbox/OneDrive/etc folders entirely, regardless of if the files are stored locally or not.
The whole "just sync everything, and if you can't seek everything, pretend to sync everything with fake files and then download the real ones ad-hoc" model of storage feels a bit ill-conceived to me. It tries to present a simple facade but I'm not sure it actually simplifies things. It always results in nasty user surprises and sometimes data loss. I've seen Microsoft OneDrive do the same thing to people at work.
The primary trouble I have with backblaze was that this change was not clearly communicated, even if perhaps it could be justified.
That doesn't really make a lot of sense, though. Reading a file that's not actually on disk doesn't download it permanently. If I have zero of 10TB worth of files stored locally on my 1TB device, read them all serially, and measure my disk usage, there's no reason the disk should be full, or at least it should be cache that can be easily freed. The only time this is potentially a problem is if one of the files exceeds the total disk space available.
Hell, if I open a directory of photos and my OS tries to pull exif data for each one, it would be wild if that caused those files to be fully downloaded and consume disk space.
This is a complexity that makes it harder, but not insurmountable.
It would be reasonable to say that if you run the file sync in a mode that keeps everything locally, then Backblaze should be backing it up. Arguably they should even when not in that mode, but it'll churn files repeatedly as you stream files in and out of local storage with the cloud provider.
Unless it does something very weird it won't trigger all those files to download at the same time. That shouldn't be a worry.
And, as a separate note, they shouldn't be balking at the amount of data in a virtualized onedrive or dropbox either considering the user could get a many-terabyte hard drive for significantly less money.
Shoutout to Arq backup which simply gives you an option in backup plans for what to do with cloud only files:
- report an error
- ignore
- materialize
Regardless, if you make it back up software that doesn’t give this level of control to users, and you make a change about which files you’re going to back up, you should probably be a lot more vocal with your users about the change. Vanishingly few people read release notes.