[j-nsp] MX960 PEMs and 3 phase power

[Mark Tinka]

On 3/23/23 10:29, Gert Doering wrote:

> "typical" data centres over here have 2 primary feeds, either one
> with UPS and one with generator, or both with (different) UPSes - but
> depending on the load drawn by a rack, might be presented as multiple
> circuits with 16A each, and individual circuit breakers.

Same here, and also what we have seen at most of the larger data centres 
we work with.


> Now, if another device next to your MX960 has a PSU failure and kicks
> one of the circuit breakers, what do you want your MX960 to do...  as
> well, what do you want to happen if the UPS fails, and one of the primary
> feeds goes down.

We typically deploy a full power complement in all our routers to 
protect against issues such as these, even when we may not necessarily 
need all that power Day 1.


> We do not have MX960s, but we did have other devices with 3 PSUs that
> needed 2 to fully power all line cards, and this was quite a bit annoying
> - "it says redundant PSUs, but no full feed A / feed B resiliency"...

Even with the 2nd generation high-capacity AC power supplies, the MX960 
requires at least 2 power supplies at a minimum, to power the 2 zones in 
the system.

These power supplies have 2 receptacles per unit, to allow you to drive 
a full chassis running at speed with just 2 of them in the box. 
Otherwise, with just a single receptacle per power supply, you only get 
about half of the energy out of the power supply.

Mark.