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    Depending of your setup, all our COs are setup to provides A+B
feed.  Which include TS, UPS and Bypass.

    PS: Be sure to test before putting it in production, the PEM #, and
its assignment into the chassis, are not that straight forward.

-----
Alain Hebertahebert@pubnix.net
PubNIX Inc.
50 boul. St-Charles
P.O. Box 26770 Beaconsfield, Quebec H9W 6G7
Tel: 514-990-5911http://www.pubnix.net Fax: 514-990-9443

On 3/22/23 11:27, Tom Storey via juniper-nsp wrote:
> 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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On 23/3/23 2:27?am, Tom Storey via juniper-nsp wrote:
> 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?

Start by going back to "if that phase drops", depending on where you are
and how much load you present using any non-trivial amount of power may
not be acceptable.

Then even consider if loss of a single phase is even a plausible outage
that isn't going to mean a full loss right afterwards.
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On 3/22/23 17:27, Tom Storey via juniper-nsp wrote:

> 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?

I can't think of any plausible reason why this would not work, but it
sounds awfully complicated.

If you are in a typical data centre, all your power is going to come
from at least one UPS anyway, maybe even two. So not sure you need to
worry about this.

Mark.
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Hi,

On Thu, Mar 23, 2023 at 06:01:07AM +0200, Mark Tinka via juniper-nsp wrote:
> If you are in a typical data centre, all your power is going to come
> from at least one UPS anyway, maybe even two. So not sure you need to
> worry about this.

"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.

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 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"...

gert
--
"If was one thing all people took for granted, was conviction that if you
feed honest figures into a computer, honest figures come out. Never doubted
it myself till I met a computer with a sense of humor."
Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany gert@greenie.muc.de

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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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.
> _______________________________________________
> juniper-nsp mailing list juniper-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp
>
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On 3/23/23 14:15, Tom Storey via juniper-nsp wrote:

> 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.

Right, data centre providers will deliver power to your rack either via
a single- or 3-phase bus, and leave you to decide how to use it.

Unless you are doing something special with the data centre provider for
you to yield the desired outcome, I'm not sure splitting phases across
the chassis adds any more value than A+B, especially with the MX960
power supplies which come with 2 AC receptacles per power supply that
you, ideally, will already split to redundant power sources.

Mark.
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