I recommend not trying to be smart about what directories to backup, but just backing up all regular partitions.
I don't recommend backing up the files in /var/lib/mysql though, at least not as your primary way to back up MySQL databases, as they are not guaranteed to be in a consistent state when you back them up. I recommend doing SQL dumps and backing up those.
I am not trying to be smart.
It is pointless to backup the OS. The point of backup is in case of a disaster such as hardware failure or in the event a site was hacked to be able to restore recent data and in the fastest possible time.
I have created a kickstart in order to minimize the install time of the server in case the disaster strikes.
The /etc is very usefull as it contains many changed configurations you may have done on the server.
Offcourse I do not copy the mysql files since if you need to do so the database must be stopped for consistency reasons. I use mysqldump and I also make a bz2 of the dump so the database backup is as small as possible.
But the point here is not to argue. We all know the issues that arise. The point is to discuss them and maybe create our own way of taking an effective plesk backup.
I currently do the following to reduce the load on plesk. I take a backup on the server repository and then I rsync the dumps partition to a remote site. I stopped the ftp backup procedure since it was killing the server.
Still my DR time is approximately 4 hours to 100% restoration.
I am seeking ways so we can all benefit a fast and secure way to backup plesk which will fully or at most part bypass plesk. After all what plesk does in order to backup is not rocket science...
It needs some time and effort in order an alternative way to be built but it is not impossible.
I have also written a script to backup non control panel servers which runs perfectly and uses ncftp to send files to ftp.
The load is minimal, it does logging which emails it to me and it consists of simple shell commands.
Can we do the same for plesk maybe ?
PS : The prices some companies ask for backup is crazy ! I would have paid myself for a ready made solution for plesk backup but I do not believe the ammount of money they ask is justified for what they sell. I feel they are ripping me off when they request 400-500usd for a single server. If I am to pay so much money I will pay 1000$ and get a much better solution from the market which will backup not just one plesk server but many.