ASR 9010 Redundant Power

[Lyphiard]

On one of Cisco's live webcasts, a diagram is shown where in an ASR 9010, feed A is connected to the three power supplies on shelf 0 and feed B is connected to the three power supplies on shelf 1.

The webcast also mentions that if all of the power supplies in a specific shelf fail, the shelf itself will go offline and the system will not be able to detect the presence of the failed/unpowered power supplies.

Is there a specific reason as to why it's recommended that each power shelf have an individual feed, as opposed to say having feed A on one PSU and feed B on two PSU's on shelf 0, then vice versa for shelf 1? This way, the system will be able to detect the presence of failed power supplies as well has have a bit more redundancy (ie. in case both a shelf and a feed fails at/near the same time).

[Aleksandar Vidakovic]

The whole chassis is a single power zone. There are no restrictions to the way power feeds are connected to power supplies. If find the statement from that webcast very surprising. Can you share the URL? I would like to verify the source of that information. 

/Aleksandar

[Lyphiard]

Hi,

Webcast is on YouTube here: https://youtu.be/mBQYmE5bJA0?t=779

[Aleksandar Vidakovic · Accepted solution]

Ah, that's Xander's old video way back from 2013. :) 

I think you misunderstood what Xander wanted to say. If PS3 is the only power supply in power shelf 1 and it fails, the system won't know whether there is no PS in shelf 1 or whether there is a failed PS in shelf 1. That much is true. However, Xander also said that there is no restriction on how you insert the PSs. So the diagram showing feed A going into shelf 0 and feed B into shelf 1 is not in any way illustrating a restriction or recommendation. Your suggestion makes a lot of sense. 

Also, all PSs on asr9k have two feeds, so you can consider having two feeds going into each power supply. Depending on the AC/DC type and generation (i.e. version) of the PS, two feeds in a single PS give you either 1:1 redundancy or allow you to achieve the full power out of the PS. BRKARC-2003 from Cisco Live 2015 have more details about this.

/Aleksandar