On 25/07/2019 20:39, John Pierce wrote: > On Thu, Jul 25, 2019 at 10:32 AM hw <hw at gc-24.de> wrote: > >> I can't help it when the primary name server goes down because the UPS >> fails >> the self test and tells the server it has 2 minutes or so left in wich case >> the server figures it needs to shut down. I wanted better UPSs ... >> > critical infrastructure servers should have redudant PSUs, on seperate UPSs. Separate DNS servers must be on a different subnet according to RFC2182 (https://tools.ietf.org/html/rfc2182): Secondary servers must be placed at both topologically and geographically dispersed locations on the Internet, to minimise the likelihood of a single failure disabling all of them. I know that UPSs are physical, and subnets are logical, but the reasoning behind the requirement is due to having to be on a different infrastructure.