Google Backup and Sync – potential disaster? How does it operate?

Does anyone actually know how GB&S actually works?

Not for the first time, I have had to put a block on the use of this tool. Because I have witnessed it deleting a file on my main machine which it shouldn’t have deleted, and which is a vitally important file. Fortunately I have redundant backup arrangements, and have been getting quite suspicious of GB&S recently, so taking things defensively.

I believe the reason it deleted it is because I am attempting to keep two machines in sync with one another through their use of GB&S using a shared Google Drive. Although I have found nothing definitive out there which says you shouldn’t do that, I’m pretty much convinced now that that is a sure route to disaster and intend to stop forthwith.

And it isn’t helped by the fact that I can find absolutely no information whatsoever about how GB&S determines which end (i.e. Cloud-based Drive space, or local machine) is definitive, in terms of whether a file should be deleted or kept.

So the problem seems to be that machine A had this file, now deleted. But then I connected machine B, which I hadn’t used for about a week or so. The idea was that machine B would “sync up” to what it found in the Cloud (Drive) space. But what it appears to have done in some cases (as you can see, I am floundering to find out what rules it might be following) is to have decided that the Cloud (Drive) space was out of date, not its own space. So it deleted some stuff, including that vital file.

You might expect that dates, such as the Last modified date of a file/directory, might be involved. But I haven’t been able to find any proof of that either way.

Even using GB&S with just a single machine, you have the option, if you so choose, of deleting a file directly in the Cloud (Drive) space, in which case you would then expect, next time GB&S was operating, that file to be deleted in your local machine. But, at the moment of discovering that discrepancy, how does GB&S know which way to sync? (i.e. delete from machine, or upload the file to the Cloud (Drive) space).

Any info/pointers/links greatly appreciated.