you could unplug the HDs before you reset.... but even then you should back up... which is funny because I use the 323 as a back up... imo
First - not everyone uses their DNS-323 to store backups - and second - whether or not you choose to back up your backup is your business - but let me explain it this way ...
In the days when backup was done to tape, chances of data loss due to a failed backup system were
relatively low, if the tape drive failed, you simply replaced the drive and stuck the tape in the new one, and if the tape itself failed, there would usually be another one a day or so older, assuming that a backup strategy such as grandfather/father/son was being used - so the risk of data loss was not
that significant.
A lot of SMB backups are now disk-to-disk (D2D) - I won't elaborate on the reasons which are essentially cost and speed - however there is a very real risk of the disk failing and the backup data being lost - even with the grandfather/father/son strategy, all the backup data sets are stored on the same drive, so if the drive fails, all the backups are lost.
What's the chance of your primary drive failing at the same time your backup drive fails?