SRL Archive - Technology

I have been using Google's DNS server (8.8.8.8 and 8.8.4.4) but every now and then (about once every few months) it will go offline.

So i'm wondering if the purpose of a secondary DNS is for backup, shouldnt we set the secondary DNS to be from a completely different provider than that of the primary DNS, since there's a much smaller chance that 2 different DNS provider went down together than the primary and secondary DNS of the same provider went down?

I use 8.8.8.8 (Google) for my primary and then 208.67.220.220 for my secondary (OpenDNS) or 4.2.2.2

So it's indeed better for the secondary DNS to be from a different provider?
Never seen anyone mention it in those articles so i thought there's a catch to it.

When creating DNS servers, best practices is to run them on different networks so if your DNS Server 1 goes down, DNS Server 2 will still be running, but if they are on the same network (EG: same data center) and that data center loses network access for whatever reason then both DNS servers would fail, having DNS1 with Google and DNS2 with OpenDNS won't effect you, in fact you've added a failsafe, there is no catch AFAIK