Redundant Sup Power Reserve Question (6500)

[Antonio Knox]

I know that the 6500 with a Sup 720 reserves power for a redundant 720.  If there is no plan to install that redundant Sup, is there a means of releasing that reserved power?  I know that one approach would be to insert a card into that slot to cut the reserve down, but I need to reclaim all of that power.  Any ideas or useful links to assist, folks?

[Antonio Knox]

I'll repackage the question:  I have a 6506 in power mode 'combined', which nets me 1952.16 Watts.  I want to run my supplies in 'redundant' mode, but with 1306.62 Watts of system power used (315 watts reserved to a nonexistent redundant Sup), I'm concerned that when the switch to 'redundant' power mode is made that I may lose an existing blade due to power deficit. 

It is my understanding that when there is a power shortage, that power is taken from slots from the bottom up, skipping the Supervisors.  The questions become the original one in the OP as well as: If I move the switch into redundant mode, will the power remain reserved for the redundant Supervisor or will it be released and distributed among the existing modules.

[Raju Sekharan]

You cannot release the power allocated to standby supervisor

[Arumugam Muthaiah]

Hi Antonio,

When you configure redundant mode power supply, the single power supply will take care the entire switch.So both power supplies should have enough power. In the event of a failing power supply that leaves the system without enough power to drive the total configuration, inline devices and line cards will be shut down by the power management software to fall within operating power capabilities.

In order for the user to recognize the event and its consequences, the shutdown sequence logic should be known and understood: in particular, the Catalyst 6500 control software will first start to power down inline devices from the highest numbered port to the lowest numbered port, then from the bottom slot up. If after powering down all inline devices there is still insufficient power, the system will start to power down line cards from the bottom slot up with the exception of the supervisor module and of the services modules (that is, firewall module, VPN module, IDS module, and so on). Supervisor and services modules are the last modules left operating. For this reason, important hosts should be plugged into ports on the top-most modules (that is, slots 1, 2, 3, and so on) and from the lower numbered ports up. It is worth noting that the order of shutdown is fixed by the system and cannot be changed

Refer:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_white_paper0900aecd805457cc.html

Regards,

Aru

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[Antonio Knox]

Arumugam,

I know how it works in theory, but what I'm trying to understand is this, if I configure redundant mode, I would have enough power to run all of my EXISTING line cards if the 6500 wasn't reserving power for the NONEXISTING redundant Sup.  I other words, if not for the reserved 315 Watts for the redundant Sup (which does not exist and will not exist on this 6500), I would have no concerns for moving to redundant mode, because power usage by EXISTING line cards falls below the capacity of one power supply. My actual Sup is in slot 5, power is reserved in slot 6.  Will the reserved power for the NONEXISTENT Redundant Sup remain held and push my usage over the capacity of one power supply, and therefore cause EXISTING line cards to shut down because the 6500 is not acknowledging EXISTING line cards power requirements over NONEXISTENT cards?

[Arumugam Muthaiah]

Hi Antonio,

Sorry, i misunderstood your question initially. But it is clear now.

As Rajs said, the power is reserve for a redundant supervisor even if there is not one present. In the case where there is a linecard in the redundant supervisor slot, The power will be allocated for either the linecard or the redundant sup (whichever is greater).

The switch will be allocating enough power from the power budget to power a redundant supervisor. If you place a linecard in the redundant supervisor slot that does not need as much power as a supervisor, the linecard will just draw what it needs.

Regards,

Aru

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[Antonio Knox]

What if I don't have anything in slot 6.  See below to better understand my issue.  What happens if I switch to redundant mode?  Do I lose power to one of my existing line cards because the power reserved in slot 6 gets held? Notice that if I didn't have 315 Watts reserved in slot 6 I could run redundant power and not be concerned about losing power to any of my line cards.

Switch#sh power

system power redundancy mode = combined

system power total =     1952.16 Watts (46.48 Amps @ 42V)

system power used =      1306.62 Watts (31.11 Amps @ 42V)

system power available =  645.54 Watts (15.37 Amps @ 42V)

                        Power-Capacity PS-Fan Output Oper

PS   Type               Watts   A @42V Status Status State

---- ------------------ ------- ------ ------ ------ -----

1    WS-CAC-3000W       1171.38 27.89  OK     OK     on

2    WS-CAC-3000W       1171.38 27.89  OK     OK     on

                        Pwr-Allocated  Oper

Fan  Type               Watts   A @42V State

---- ------------------ ------- ------ -----

1    WS-C6506-E-FAN       98.70  2.35  OK

                        Pwr-Requested  Pwr-Allocated  Admin Oper

Slot Card-Type          Watts   A @42V Watts   A @42V State State

---- ------------------ ------- ------ ------- ------ ----- -----

1    WS-SVC-FWM-1        171.78  4.09   171.78  4.09  on    on

2    WS-X6148-GE-TX      121.38  2.89   121.38  2.89  on    on

3    WS-X6548-GE-TX      132.72  3.16   132.72  3.16  on    on

4    WS-X6408A-GBIC       84.00  2.00    84.00  2.00  on    on

5    WS-SUP720-BASE      315.00  7.50   315.00  7.50  on    on

6    (Redundant Sup)       -     -      315.00  7.50  -     -

[Arumugam Muthaiah]

Hi Antonio,

Thanks for your kind response. I verified the same in LAB and dont have standby supervisor on slot 6. But still power 363.30W is reserved for standby supervisor, even if we are not using it. see the detail below,

Switch#sh module switch 1
Switch Number:     1   Role:   Virtual Switch Active
----------------------  -----------------------------
Mod Ports Card Type                              Model              Serial No.
--- ----- -------------------------------------- ------------------ -----------
  5    5  Supervisor Engine 720 10GE (Active)    VS-S720-10G        SAL1601054T

Mod MAC addresses                       Hw    Fw           Sw           Status
--- ---------------------------------- ------ ------------ ------------ -------
  5  e05f.b947.8e69 to e05f.b947.8e70   4.0   8.5(4)       12.2(33)SXI7 Ok

Mod  Sub-Module                  Model              Serial       Hw     Status
---- --------------------------- ------------------ ----------- ------- -------
  5  Policy Feature Card 3       VS-F6K-PFC3CXL     SAL16010258  1.2    Ok
  5  MSFC3 Daughterboard         VS-F6K-MSFC3       SAL1552ZL99  5.1    Ok

Mod  Online Diag Status
---- -------------------
  5  Pass

Switch#sh power switch 1 
Switch Number: 1
system power redundancy mode = redundant
system power redundancy operationally = non-redundant
system power total =     2331.00 Watts (55.50 Amps @ 42V)
system power used =       876.96 Watts (20.88 Amps @ 42V)
system power available = 1454.04 Watts (34.62 Amps @ 42V)
                        Power-Capacity PS-Fan Output Oper
PS   Type               Watts   A @42V Status Status State
---- ------------------ ------- ------ ------ ------ -----
1    WS-CAC-2500W       2331.00 55.50  OK     OK     on
2    none
                        Pwr-Allocated  Oper
Fan  Type               Watts   A @42V State
---- ------------------ ------- ------ -----
1    WS-C6509-E-FAN      150.36  3.58  OK
                        Pwr-Requested  Pwr-Allocated  Admin Oper
Slot Card-Type          Watts   A @42V Watts   A @42V State State
---- ------------------ ------- ------ ------- ------ ----- -----
5    VS-S720-10G         363.30  8.65   363.30  8.65  on    on
6    (Redundant Sup)       -     -      363.30  8.65  -     -
system auxiliary power mode = off
system auxiliary power redundancy operationally = non-redundant
system primary connector power limit =   10920.00 Watts (260.00 Amps @ 42V)
system auxiliary connector power limit = 10500.00 Watts (250.00 Amps @ 42V)
system primary power used =               876.96 Watts (20.88 Amps @ 42V)
system auxiliary power used =            0 Watt

Yes, the power cant be released which is allocated for standby supervisor. We will lose the power even though, we are not using the standby supervisor on slot 6.

Regards,

Aru

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[Antonio Knox]

Just switched to redundant and didn't lose any of my line cards.  It appears that the reserved power was no longer reserved after switching to redundant mode, since doing so would have meant losing power to one of my line cards.  I hope that this helps someone in the future.

Thanks for your assistance here, Arumugam.

[Raju Sekharan]

Can you paste the current " show power" output after you switched over to redundanct mode

[Antonio Knox]

I could, but it would likely not be of much use.  I asked the question because I needed to do a power upgrade (from 110V to 220V circuits).  To do that with no service interruption, I had to move power one supply at a time.  With my current configuration, it appeared that I would lose a line card during the power upgrade if I moved to redundant mode, because:

system power used = 1306.62 Watts > 1171.38 Watts per supply.

I didn't appear to have enough power per supply to run redundant mode because 315 Watts were reserved for a potential redundant sup, and that reservation puts me over the power threshold for my individual power supplies. I don't need/want that power reserved, because I don't have a redundant Sup, instead I need that power for my line cards (none of which are in slot 6). The thinking was that without the power reservation, I would be able to run redundant mode without losing any line cards because:

1306.62 Watts - 315 Watts = 991.62 Watts

and with a total requirement of 991.62 Watts, a single power supply of 1171.38 Watts could cover demand:

991.62 Watts < 1171.38 Watts

But with a power draw of 1306.62, it can't cover demand and would have to shut down a line card to get beneath the threshold.  And as we know, theoretically the 6500 starts powering down line cards from the highest numbered slot up (skipping Sups) to get power usage below capacity.  I was hoping that the switch was smart enough to realize that power priority should go to the existing line cards over the non-existing Sup reservation if it came down to it.  In my case, the switch was intelligent enough.  Hope that makes sense.