Onsite backup - better to another NAS or to an Expansion unit?

[halloleo]

For my DS1520+ I am rethinking the onsite backup solution. (At the moment I use an external HD for this, but I want to make this HD the offsite backup).

So, in regards to the onsite backup I see two convenient options: Another (lower-powered) NAS or the DX517 Expansion unit? What is better?

 

[Telos]

Backing up to a DX is not a back-up. Back-ups are off-NAS. Google "3-2-1 backup".

 

[halloleo]

Backing up to a DX is not a back-up. Back-ups are off-NAS. Google "3-2-1 backup".

I see! The DX does not count as a separate device, right? So a cheap-ish NAS like the DS420j is better?

 

[Rusty]

I see! The DX does not count as a separate device, right? So a cheap-ish NAS like the DS420j is better?

Correct. DX unit can't work without the main DS one. Any stand alone NAS (DS) would be a "smarter" choice.