Re: [j-nsp] MX960 PEMs and 3 phase power

[Tom Storey via juniper-nsp]

We have A+B power delivered 3 phase to the racks, broken out on PDUs, but I
think I must have been thinking about another platform in regards to not
splitting PSUs across phases.

Thanks!

On Thu, 23 Mar 2023, 09:15 Mark Tinka via juniper-nsp, <
juniper-nsp@puck.nether.net> wrote:

>
>
> 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.
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[j-nsp] MX960 PEMs and 3 phase power

[Tom Storey via juniper-nsp]

Hi all.

I had this idea in my head that MX960 power supplies should not be split
across phases, but I cant find anything in any documentation that says that.

Can anyone comment on whether multiple phases per PEM are supported, or
whether its even a reasonable idea to put into practice?

My thought is one PEM on one phase, such that if that phase drops, you drop
that PEM entirely. Or is it worthwhile spreading across phases to keep even
half of a PEM alive and supplying the chassis?

Thanks
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