WP#23 - Proper Sizing of IT Power and Cooling Loads

Overview

The Green Grid's WP#23 is dated 27 July 2009 and is the joint work of ten authors from APC, Emerson, Chatsworth, Sun, Dell, Intel, IBM and HP. The paper addresses how IT power and cooling loads in data centres should be sized correctly. Its starting point is that energy costs and efficiency demands call for more accurate estimates of capacity requirements. The paper is available through a registration-based download, and this summary relies only on information from the public library page.

The paper's central argument is that nameplate-based sizing over-provisions power and cooling capacity. A gap exists between the ratings printed on the label and the power IT equipment actually draws, and that gap leads to infrastructure investment larger than needed. The paper puts this gap at the centre of the question of how the design load is derived. As the remedy, the paper introduces software tools that estimate power and cooling capacity requirements, namely vendor configuration tools and power-estimation tools. It positions them as a more accurate basis than traditional estimating methods. When equipment is selected against a known configuration, the design IT load can then be computed from a more realistic value rather than from the nameplate total.

The limit of this record is that, being based on the landing-page abstract, it cannot relay the details of the method. The message is still clear: before UPS and cooling systems are sized, the IT load should be set with measured values or values from a vendor calculator. This matters both for initial capital cost and for the efficiency penalty of running at low load.

Key points

1. Dated 27 July 2009, with ten authors from APC, Emerson, Chatsworth, Sun, Dell, Intel, IBM and HP.
2. Motivated by energy costs and efficiency demands requiring more accurate requirement estimates.
3. Nameplate-based sizing over-provisions power and cooling.
4. Introduces software tools for estimating power and cooling capacity requirements.
5. Positions these tools as more accurate than traditional estimating methods.
6. Addresses the gap between label ratings and real IT draw.
7. Free download needs registration; summarised from the public landing page.

Using it in design

• In rack and IT load entry, let users enter measured or vendor-calculator power instead of nameplate.
• Store both values (nameplate and realistic).
• Warn when the design IT load is derived from nameplate, as that typically leads to over-sizing.
• Feed the derated (realistic) value to UPS and cooling sizing.

Who should read it

Designers who derive power and cooling capacity from IT load, and engineers doing capacity planning.

Publication details

Authors

John Bean; Ron Bednar; Richard Jones; Robb Jones; Phil Morris; David Moss; Michael Patterson; Joe Prisco; Wade Vinson; John Wallerich

Publisher

The Green Grid

Year

2009

Document number

WP 23

Document language

English

Source type

Industry body

Access

Citation only

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation