[Nut-upsdev] Questions about failover architecture

[Greg Troxel]

Jim Klimov <jimklimov+nut at gmail.com> writes:

> I'd say this is not so much about "often enough" (or it would have been
> addressed earlier), but neither are ethernet cable/port outages yet people
> do LACP/trunking/bonding anyway. And "out of band" serial consoles for good
> measure.

Sure, but that's for things whose failure is a much bigger deal.  I'd
say that for power, the thing people would do is have two UPS units,
with two monitoring computers, powering dual power strips with computers
having redundant supplies.

> I assume issues that may be relevant are loss of networking (SNMP et al)
> during a power outage, when some switch goes off, and the "out of band"
> link can be used anyway to command the UPS to power cycle.

Interesting concept.  It would seem obvious that all networking has to
be on UPS to have a reasonable setup.

I was trying to ask for real examples of situations/problems people
have.  I do get the theoretical point.

> Another problem is that UPS controllers often do expose different sets of
> data points or with different precision over various protocols. Even with
> SNMP I saw vendor MIBs and IETF standard trees show the same data
> differently (e.g. as integer and as two-digit-after-the-dot floats)
> simultaneously. Merging this info (even if just for read-only queries)
> would be quite a practical benefit.

I suppose, and it's a lot of work.  Probably architecturally there would
need to be a driver plumbing object that can be hooked up to N drivers
and acts like 1 driver, and does the merging.  It would need to have
configurable strategies as there is no good single answer for how to
merge e.g. something with integer volts at a 5s rate and VVV.VV at a 60s
rate.