ASR9k :: Power supply redundancy

[Tom Marcoen]

Hey guys

Another ASR9k question from me, this time about power supply redundancy. We connected all eight power supplies on the ASR9010 as can be seen in the picture. The four connectors to the left go to feed A, the four connectors on the right to feed B.

The problem I was facing is that I only powered on one power bay (no production yet - I had to do a quick config check) and when the DC briefly lost power (I assume one of the feeds for testing), my router went down.

The question thus is, which power outlet on the back goes to tray 1 internally and which outlet goes to tray 2? Should I connect the cables like this to have feed A supply power to 2 PSUs in tray 1 and 2 PSUs in tray 2?

Second question, is there N+N redundancy or N+1? I.e. if the chassis is fully equiped with 8 line cards, do I then require 4 PSUs (and another 4 for redundancy)? Or do I then need 7 PSUs to power the chassis and I only get 1 for redundancy?

Regards

Tom

[Aleksandar Vidakovic]

Hi Tom,

asr9k has only one power zone into which all power supplies feed the power. From that perspective it doesn't matter how you connect your power supplies. We recommend to spread them out evenly (if not all power supply slots are in use) because of heat dissipation.

Not all LCs require the same power. You can use the power calculator on CCO or the "admin show environment power-supply" command to see how much power each card requires and how much is available with the given PSes.

On N+1 vs N+N redundancy, you can find this table and some more info on power redundancy in the slide deck from session CL2904 from this year's Cisco Live.

	AC V2	AC V3	DC V2	DC V3
Max Power	3 kW	6 kW	2.1 kW	4.4 kW
# of Feeds	1	2	2	2
Feed redundancy in PEM	n/a	No	Yes	No
# of PSs per power tray	4	3	4	4
Redundancy scheme1)	N+N	N+N	N+1	N+N

Hope this helps,

Aleksandar

[Tom Marcoen]

Hello Aleksandar

Thank you for your reply. However, given the ASR 9010 has two A9K-AC-PEM-V2 modules, what if one fails (assuming this is possible)? In that case, four power supplies will become unavailable. If - as on my picture - four cables from feed A supply power to this PEM-V2 module, the ASR9010 draws it power only from power feed B on the second PEM-V2 module. If then also feed B fails in addition to the first PEM-V2, my ASR loses all power.

[Aleksandar Vidakovic · Accepted solution]

Hi Tom,

power tray is passive, it has no active components. All active components are on power supplies. Your scenario would happen if feed A fails and later feed B fails. This would constitute a double fault scenario against which one possible remedy is to have one feed from some kind of UPS.

regards,

Aleksandar

[anandbhalla]

Hello Aleksandar,

Does the same applicable for ASR-9912-DC chassis also. In my case the 9912 is equipped 6 x PWR-2KW-DC-V2.

Regards..