DC power for the data center

A 2 minute battery capacity might not be enough to get a backup generator running, allowing for a couple of restart attempts. 10 minutes might be more appropriate. A rack (assuming 1KW) would require about 14Ah of battery capacity. But one battery per rack becomes a maintenance problem. Too many batteries to keep track of in a large data center. Not to mention NEC (and other) code requirements for battery installations. You might be better off with larger battery racks in dedicated rooms. But then 12V isn't optimum to distribute over a large area. 48V would be better (its a standard in the telecom industry).

Where's the battery backup (UPSs)? Everything is going to go down on momentary power bumps or while waiting for the gensets to spin up.

-- Paul Hovnanian snipped-for-privacy@hovnanian.com

---------------------------------------------------------------------- Have gnu, will travel.

On Sun, 18 Jan 2009 09:54:36 -0800 Paul Hovnanian PE wrote: | snipped-for-privacy@ipal.net wrote: | |>

|> |> While I am not fundamnetally opposed to using DC, the power system I would |> rather have in a data center building would be: |> |> 480Y/277 AC from utility to transfer switch(es) |> 480Y/277 AC from generator(s) to transfer switch(es) |> 480Y/277 AC to DC conversion unit in each rack cabinet |> Short term (2 minute) battery backup in each rack cabinet |> 12VDC from power conversion unit to each blade or board |> DC conversion to component power performed on board | | A 2 minute battery capacity might not be enough to get a backup generator | running, allowing for a couple of restart attempts. 10 minutes might be | more appropriate. A rack (assuming 1KW) would require about 14Ah of battery | capacity. But one battery per rack becomes a maintenance problem. Too many | batteries to keep track of in a large data center. Not to mention NEC (and | other) code requirements for battery installations. You might be better | off with larger battery racks in dedicated rooms. But then 12V isn't | optimum to distribute over a large area. 48V would be better (its a | standard in the telecom industry).

Although that is a standard, very very few computer board take 48VDC directly. So that means another PSU module to step 48VDC down to 12VDC.

What is needed is the batteries in each rack to be integrated into the rack-PSU. Think of it as UPS without the inverter part, all in one box.

|> The above would utilize the custom 12VDC-only computer board, such as |> those |> suggest by Google. This eliminates a separate PSU for each computer or |> blade group. |> |> If commodity computers are to be used, then I would do: |> |> 416Y/240 AC from utility to transfer switch(es) |> 416Y/240 AC from generator(s) to transfer switch(es) |> 240 AC to each rack |> IEC or Schuko power strips in each rack |> 240 AC to each computer PSU |> | | Where's the battery backup (UPSs)? Everything is going to go down on | momentary power bumps or while waiting for the gensets to spin up.

Regular 240VAC UPSes for those.