Conference netcad::hub_mgnt

From the DEChub V4.1 release notes:

New power supplies are available for the DEChub 900 MultiSwitch.
The new power supply, part number H7894, can deliver 163 watts
of power.  It is shipped with all new DEChub900 MultiSwitch hubs.
The previous power supply, H7890, delivered 140 watts.  Release 
V4.1.0 and higher of the DEChub 900 MultiSwitch firmware can utilize 
the additional power in its power allocation algorithm in some 
configurations.

Please read Section 5 of the DEChub 900 MultiSwitch Owner's Manual 
to see how a power budget is calculated from the power supplies
present in a hub, and how power supply redundancy is handled.  The 
power budget allocated by the DEChub 900 MultiSwitch for each 
power supply depends on the mix of H7894 and H7890 power supplies, 
and on the version of firmware.  The following chart shows how many 
watts of power per power supply are calculated in the power budget.      

Hub Manager           Power Supply Configuration     Budgeted Power
Version                                              per Supply
------------------    --------------------------     --------------
V4.0.x and earlier    any                            140 watts
V4.1.0                all H7890 power supplies       140 watts
V4.1.0                mix of H7890 and H7894         140 watts
V4.1.0                all H7894 power supplies       163 watts

    RE :-.0
    
    I thinbk the answer is YOU CAN MIX power supplies, but the power
    calculations in HUBwatch *MAY* fall back to the 140W defaults if you
    have mixed supplies. If you have ALL H7894's then I think it will be
    correct.
    
    MIXED supplies WILL work however...
    
    Mark

    Yes yes yes you *can* mix both types. Mark is correct, having
    a mix of H7890's and H7894's will only limit you in the total
    wattage that can be allocated. No other restriction in terms
    of hot swapping out or in of a mixed group of power supplies
    will be seen. There are no other known problems in terms of
    compatibility of the two types of power supplies that would
    prevent them from being mixed in the same HUB. I have 6 HUBs
    that I have configured with mixed power supplies and there is
    no problem other than that they all default to the 140w allocation.
    My HUB configs aren't anywheres max'd out so there are no restrictions
    visible.
    Not to worry, your customers do not have to unecessarily trade in their
    current H7890's for H7894's. You customers should have to be concerned
    about needing all H7894's if their current hub configs dictate needing 
    the extra power allocation.
    
    Bob

    How close to the limit should the new supplies/power allocation be
    pushed for reliable operation?  I have a customer who wants to put 2
    900EF's and 6 PEswitches in a hub (comes to 438 watts, 69a @ 5v, and
    7.2a @ 15v) with 4 H7894's.  Is this ok, or should I convince him to
    expand to another hub?

    Well, the 4th power supply doesn't figure into the picture until
    one of the other 3 goes down. Only 3 power supplies are actively
    figured into the  power budget at any time, and the 4th one is in
    stand-by as a backup. So the maximum power available for modules
    (at 163w each), is 489 watts minus 15w (for the HUB MAM module)
    for +5v. So that's 474 watts of +5v for the 8 backplane slots.
    I'm not going to bother figuring the 15v at this time.
    So it looks like  with your configuration at 438 watts, it should
    be fine with 4 H7894's (one as backup). It's my understanding that
    3 H7894's will supply a true 489 watts. There's probably some actual
    head room for what the power supplies can provide. It's the allocation
    algorythm which sets the limit at 489 watts of +5v, not what the 
    power supplies can probably provide. So as long as you have some
    combination of modules which need 474 watts of +5v or less, the way
    I see it, it should be configurable in a hub with 4 H7894's.
    
    Bob

    RE:  .last 2
    
    I just had the exact same config come up at Oracle and I did the +5,
    +12 and Total watts calculations for the H7894's. Works just fine.
    
    
    Mark

        I'll add that when we did the qualification testing on the new
    H7894 supply, we had hubs running at 489 watts (some even slightly
    higher) at 50 degrees C for many weeks. This testing was done with 
    a mixed set of H7890 and H7894 supplies. Yes, we pushed the H7890's
    to a power output similar to the H7894 for this test. I don't see 
    any reason that you can't use the HUB to it's power limit of 489 watts
    for three H7894's or to 420 watts for a mix of H7890's and H7894's.
    If the MAM let's you power up the system after allocating power, then
    you should have no problems running it that way indefinitely.
    
    Regards,
             Bob

    Thanks - I'll tell them to let it bu....uh.. fly  ;-)