While synchronizing directories Backit Down copies, moves and deletes files. The analysis and file operation processes have been heavily tested and debugged (which doesn't exclude any bugs possibility - sorry). Besides that you have an opportunity to cancel file operation after the analysis is done and before the actual file transfers.
But the program can't know all your intentions when the matter concerns file deletion: you can incidentally delete the needed ones. If you miss something you'll lose data or on the contrary get outdated files circulating all over your computers and media untill you take a real file-hunting.
This section of the manual is dedicated exactly to these aspects of using Backit Down. So, the obscure dangers may be like:
If you decide to remove a file in a directory to be synchronized and put there another one with the same name, please, mind the following.
If newly created file is older then the deleted one (it happens if you copy this from somewhere), it will be overwritten by the removed version on the next medium-to-computer synchronization. Indeed Backit Down will consider it outdated. There is no way to tell the program it's quite a different file - Backit compares the file timestamps only, but not the contents.
There is a simple solution. You can change something in the created file: for instance run a "touch" command (on Linux) or add and remove just single space character in the file (well, if it's a textfile) and save it (on Windows).
If you've chosen to use Backit Down then use it and (if you can) leave alone other synchronization means in the folders which are included to the Backit Down projects. That is transferring files with the use of USB-drives manually, without Backit Down.
Otherwise you can forget which files where and when did you copy/move. This will reduce to zero all Backit Down reasons to exist.
Supposing there is a file you have to work over at work and at home. After the work day is over you copy it to a USB-flash drive and returning home copy it to the home computer. At morning you do the same in other direction. Once you forget to do the "evening-coping" and have to work over the outdated "home-version" discarding the changes you've made at work. In the morning you'll have two versions of the file any of which may contain valuable data abcent in the other version. Everything is still under controll. But if you forget to copy the file once more or replicate the situation with another pair of files and then another - you'll have the real problem.
Backit Down has been conceived to manage problems of this kind. But let's diversify the described situation. If you generally use Backit Down but happened to copy a file manually, then forget to copy new version back, you get a chance to:
So resuming the beginning of the chapter: if you use Backit Down, then use it constantly.
If you mix up the direction of the sync-deletion you'll lose some of your files. But if you don't use sync-deletion at all you have a chance to get a headache tracking and nailing deleted files which float up here and there.
The first case is clear. For instance, you selected a copying computer->medium with sync-deletion on the medium. If there are files on the medium which've got there from some other computer but don't exist on this one, they will be deleted.
The second variant of the piece is not so dangerous but fraught with unexpected resurrection of the files which rested in the Lord long ago. Supposing a situation: there are files on the medium which you (intentionally) deleted on this computer. If you run a medium->computer synchronization they will reappear on the same place you given them last farewell.
If you delete a file from the Backit Down project-tree you need sync-deletion. But before all, make sure you have absolutely all files that you need on the source of the synchronization (either computer or the medium) and at the same time none of those you needn't. The following procedure is recommended.
Supposing you have to remove some files (within a project) on the computer. First of all run a synchronization medium->computer (yes, backwards). Then study the project tree and remove the files you wish. Only after that you can safely synchronize computer->meduim, syncing deletion on the medium.
There is no need to resort to such procedure while you just add or modify files in the project. But they are virtually necessary if you delete files.
So, the sync-deletion is fearul but helpful. Just deleting files is also. Eventually, the operating system asks for strictness of your intention if you remove a file - remember the "Are you really wish to remove this file" dialog. That's a safety-latch. There is one in Backit Down too:
The synchronization is split on two stages not in vain. This is done exactly for you to be warned of the changes Backit Down plans to make. You are encouridged to use a filter if the actions list is too large.
Don't forget to look the list through before you click "OK"! It's the said safety-latch!