Backup and Sync, my recommendations.

I just come out from reorganizing the backup of my main two pc's. The operation was somewhat troublesome. Backup & Sync is a nice piece of software, but it's far from perfect, I had to face various weird behaviors, but I figure out how to circumvent these. I hope that the team at WSA will improve the sw, but in the meanwhile these are my recommendations for successfully using B&S. I hope that these notes will be helpful for the development team for focusing the problems and to you for avoiding them.
 
1) Avoid B&S of very complex directory trees. In fact, when I attempted this I found that the copy was incomplete, only some files were copied!
 
2) Therefore I recommend to pack your files in archives, using some utility for producing a local backup (e.g. I used AOMEI Backupper), and then backup on the cloud the archives. This will also save you a lot of space.
Saving space is fundamental, not only because it's limited, but because uploading a large amount of data is very time consuming, given common connection speeds.
 
3) Therefore my recommendation is to use maximum compression, it's worth it!
BTW, doing the backup of normal or compressed directories (in Windows) it's the same, this is transparent for the OS and so is for B&S, what counts for B&S is the uncompressed size of the files.

 
4) Split your archives in small pieces, e.g. no more than 100 MB. In fact if it happens that you suspend or hibernate your computer, B&S would not resume uploading the last files from the point were it was, it resumes uploading the last files from scratch, thus it's better not to have very large files to upload.
 
5) Don't reboot while a backup is under way! The chances of having your whole database in the cloud corrupted are high. This is what happened to me (I got “Error retrieving data” in the home page, and when I tried to access them I got an error 400, Bad request.). Unfortunately there are not commands to stop or suspend a backup and resume it, to manage these situations.
 
6) However don't desperate! The situation was only temporary fully compromised, in fact I found, a few hours later, my files restored to a previous state, with some directories that I had already canceled that reappeared, etc. Anyway, I was happy that not everything was lost. I made some cleanup, but I realized that it takes a while for Backup & Sync to update and reach a”steady state”. The situation was not coherent for a while, with differences among local info on my pc's and information on the cloud. Some sync directories reappeared again (!?) and I had to delete them twice! A strange situation indeed. However, after some troubles I had apparently everything OK. Therefore I added the new directories that I wanted to backup on two pc's and clicked the “Backup now” button.
On one pc the file transfer started normally, but on the other one it refused to backup a directory that was on the list. I pressed “Backup now” several times, as this was effective sometimes to make the backup start (!?), but this time no. I made this dir a sync dir, and “magically” it started the file transfer.
However another problem came out: the sync dir (the one last added) apparently was never ending synchronization, as soon as the upload was completed... it restarted again from the beginning! The files were not changed, so there was no apparent reason for this to happen. I feared the presence of some bug which was causing an endless loop, but this could also be due to transmission errors. Luckily, after having uploaded the files 2 or 3 times, it finally said “Complete”, “all files are fully synchronized”... but what a trouble!