What is this Google Backup and Sync "Back up your files" dialog asking?

Google Drive recently became Google Backup and Sync, and this dialog started occasionally popping out of its menu bar item:

I don't have a "Boot OS X" folder that I'm aware of, in Google Drive or locally. When I look at the settings for Google Backup and Sync, I don't see anything about this. I haven't touched the settings since it was Google Drive, so it's set to sync my Google Drive and nothing more.

I can't tell what the files are from the little generic icons, and I can't figure out how to get a list. It's also not clear what device it's talking about, or what choice it's going to remember (since the options are essentially "yes" or "later").

Does anyone know what this dialog is about and what I might have done to cause it?

Solution 1:

If you have an encrypted Time Machine backup disk, there is a hidden Boot OS X partition located on it that contains a recovery OS, allowing you to decrypt and boot from the backup in case you need to restore it from scratch. You can see this partition if you run diskutil list from the command line:

/dev/disk3 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *4.0 TB     disk3
   1:                        EFI EFI                     209.7 MB   disk3s1
   2:          Apple_CoreStorage Time Machine            4.0 TB     disk3s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk3s3

Time Machine will occasionally mount this partition while making a backup. It looks like Backup and Sync thinks this is a normal external USB drive and offers to sync it, which I suspect is a bug.

Solution 2:

Yes, you can have no "Boot OS X" folder now, but if you backup these files to cloud, there will be such a folder containing these files. The most probably cause of this dialog is due to the update from old Google Drive to new Backup and Sync changed your source settings automatically though you didn't do by yourself. Thus, better check out your current settings to find out. If it is what i guess, then uncheck the related source folder will terminate such dialog. Best wishes!