I finally found the time to protect at least some partitions by a RAID1 array.

debian:/home/max# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md2 : active raid1 sda7[2] sdb7[1]
50395776 blocks [2/1] [_U]
[=======>.............] recovery = 36.1% (18207488/50395776) finish=6.5min speed=82215K/sec

unused devices:

Why not the whole disk? Well, for my root partition I, at least for now, prefer backing up my data manually. As RAID1 protects my data from a failing harddrive, it does NOT protect it from a failing user (i.e. me). So if I accidently delete something important (who knows), I can at least restore it.