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Drama-free vent: I miss when 1U meant something

Datacenter Talk by MARIA3 21 replies 2.8K views
MARIA3

Member OP

7 #1

I miss when 1U meant something. Now they sell me 2.5kW box in 1U and my floor loading is crying. We have to make a server up with double rails and still I worry about noise. Before was 1U = 300W, nice and predictable. Now marketing team broke everything. I put three of these in rack and facilities manager wants to kill me. Regards

siesta first, deploy later
marcus_qc

Member

#2

MARIA3 said:
My floor loading is crying
Lol this is why I just run IIS on standard 2U boxes and call it a day. Active Directory doesnt care about your floor loading. But yeah the 1U thing is wild now, I saw a 4kW box advertised as 1U short depth the other day

42U and still growing
FlowSana

Member

SRE

#3

  • The original EIA-310-D specification defined 1U as 1.75 inches vertical space, with no thermal or power constraint.
  • Current H100-based nodes draw 700W per GPU, with 4-GPU configurations in 1U reaching 2800W+.
  • Floor loading for a standard 42U rack at 2.5kW per 1U would exceed 100kW, requiring reinforced slab specifications (typically 250-300 lb/ft²).

Recommendation: Specify actual power density (kW/RU) in your RFQs rather than relying on legacy form factor terminology.

It's always DNS. Always.
Doug

Member

New Jersey

#4

@MARIA3 fighting facilities managers since 2019

grabs popcorn, checks /r/drama
TE

Member

#5

100kW in a single 42U rack? That's not standard slab anywhere

kat_fold

Moderator

Moderator

#6

Legacy form factor terminology is basically useless now yeah

~be kind or be gone~
marcus_qc

Member

#7

4kW in 1U short depth lol

42U and still growing
BL

Member

#8

FlowSana said:
Specify actual power density (kW/RU) in your RFQs
This. We learned this the hard way after signing for "1U optimized" nodes from a white-label vendor. Turned out optimized meant "we removed the heatsink fins to make it fit."

garykwh

Member

Inference on a Budget

#9

FlowSana said:
Current H100-based nodes draw 700W per GPU
And that's just the GPU. Add host CPU, NVSwitch, fans screaming at 15k RPM. I measured 3.1kW at the wall for a "1U" system that was supposed to be 2.4kW typical. My Kill-A-Watt has seen things.

CUDA cores are my love language
FlowSana

Member

SRE

#10

garykwh said:
3.1kW at the wall for a "1U" system
Vendor spec sheets list GPU TDP, not system TDP. Common trap. Always ask for PSU rating and typical draw, not "up to" numbers.

It's always DNS. Always.

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