a.root-servers.net power issue (why there are 13)

[Sean Donelan <sean () donelan com>]

The NSI data center housing one of the root servers,
a.root-servers.net, lost utility power today. Reportedly
an outside utility transformer was damaged.

Generators come on-line, and the servers remained up.  NSI
didn't show any loss of traffic, however a couple of ISP MRTG
graphs of ping status did indicate a brief 15 minute network
interruption.  This may indicate an external issue, i.e.
outside of NSI, such as a network re-route or flap.  On
the followup investigation, folks may want to check if there
was a piece of equipment which wasn't plugged into where
they thought it was.  NSI has several different provider's
networks into their building, so a proble with one network
wouldn't affect the others.

Matrix (average.miq.net) shows overall the combination of
the dns-root servers stable, and relatively unchanged.

In general, the root-server design is robust; and even if
one root-server completely failed, the affect would be
minor for several days.