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C Class Power Requirements - Wow!

fishmn
Regular Advisor

C Class Power Requirements - Wow!

We are currently researching power requirements for putting these enclosures into our general server rack population. Our initial assessments put worst case scenarios at 208VAC/25+amps per enclosure. We are looking at spec'ng dual 60amp single phase (can't do 3 phase) redundant circuits to each 42U rack. I'm looking at the HP E7684A PDU ftp://ftp.compaq.com/pub/products/servers/proliantstorage/bcs-rackandpower/datasheets/ds_e7683a.pdf. Even with this doubling of power to our racks we're only looking at being able to put 2 C Class enclosures per rack + a few servers.

What are other people doing to accomodate these monsters? How have they changed your HVAC requirements? Could you put two rack rows (7 racks/row with exhaust facing each other) with C Classes in each rack and not melt down your data center?

Thanks for any input on this as we're struggling to find a way to fit these guys in. The sort of nice thing about P classes is they required their own specific 3phase power and specific engineered racks.. now we're looking at C Class as just another "server".. albeit a thirsty one!

Ron
8 REPLIES
Oleg Koroz
Honored Contributor

Re: C Class Power Requirements - Wow!

most of documentation and quick specs show maximum consumption and output, what you can do is check trough enterprise calculator see actual number, select configuration that you planning to have.

Also same rack used for p-class and c-class, different only with enclosure size. And with p-class you can make with 1 Phase 3U power enclosure 4PSU or Phase 1U power enclosure 6PSU.

Take a look for HP BladeSystem Sizer
http://h71019.www7.hp.com/ActiveAnswers/cache/347628-0-0-0-121.html

p-class Power
http://h18004.www1.hp.com/products/blades/components/powersubsystem.html
fishmn
Regular Advisor

Re: C Class Power Requirements - Wow!

Thanks.. I've worked with the sizing tool. It Gets a little mind numbing plugging numbers into it.

We have to redesign our rack power and have to design for worst case scenario (fully populated with BL685's for example).

Any real world experiences out there with the C Class?
Dave Thomson
Super Advisor

Re: C Class Power Requirements - Wow!

Hi rona

I didnt look at the power requirements :) i just installed a 16blade c-class in an Eva3000 cabinet with another 2 dl380's

If you can be more specific on what you would like to know, i can ask our electrician the questions you put forward.

Where i work its the electricains job to sort out the power.

Cheers
fishmn
Regular Advisor

Re: C Class Power Requirements - Wow!

Thanks Dave,

Can you put 2 chassis per rack in your config from a power and cooling standpoint?

We are trying to decide how best to deploy these things. We plan to use them as our platform of choice but the power and cooling requirements seem daunting. We have to wire our racks in a redundant configuration for power. Currently that means two 30 amp circuits which will generally support a full 42U rack of "normal" servers (DL385/585).

The calculations I (and HP)have done thus far with HP's power calculator show as I said prevously, a loaded C class drawing as much as 25amps or more alone. If we want to make the best use of rack space we'd like to be able to get two c classes per rack + a few servers. By my calculation that puts us into the 60amp class of PDU X 2. That size PDU is not easy to come by.

My facilities folks are balking at the idea of this much power to a rack.
Ron
Thomas Bauer_3
Frequent Advisor

Re: C Class Power Requirements - Wow!

Hi Rona,

we also researched the power requirements with the sizing tool.
This was no good idea for us.
All data were wrong.

The current power needed is much higher as is was in the sizing tool!

Be careful with data given in the sizing tool.
Better is to proof also the data of the quickspecs.

Hth
Thomas
Rob Leist
Occasional Advisor

Re: C Class Power Requirements - Wow!

We were having similar struggles with power and deciding between the single or three phase units.

If you go by the ratings of the power supplies/chassis you would need a 3 phase 60 amp circuit/PDU for two chassis, 2 PDUs if you want AC redundancy.

But if you use the power calculator and populate the chassis with beefiest equipment available now that same 60 amp PDU (17kW) will power four chassis. Once again add a second PDU for AC redundancy. That's the approach we're taking

Heat is another issue. Just make sure you got the air flow and chiller capacity. Remember that heat out is proportionate to power in.
fishmn
Regular Advisor

Re: C Class Power Requirements - Wow!

So you're basing your design on the power calculator or real world? We've had a demo c class for a while but have not had time to run it through the paces much. It is an amazing piece of equipment. I think it would be prudent to populate any chassis with a mix of blades and not fully "max out" the chassis with say max'd out 685's.

I'm still fighting the fight to get dual 60amp 3 phase and with any luck over the long run get liquid cooled racks so we could confidently put 4 enclosures/rack.
fishmn
Regular Advisor

Re: C Class Power Requirements - Wow!

We've settled on 3 enclosures per rack as our standard.