Data Center Terminology Continued

Power and cooling density:

-         Power and cooling were defined as w/ft2 or W/m2 or British thermal units (BTU)/hr or KW/hr, but the true density should be determined by KW/rack.

-         High density is above 10KW/rack.

-         Medium density is from 4 KW/rack up to 10 KW/ rack.

-         Low density is up to 4 KW/rack

-         Previously the measurement of cooling was by Tons

-         Tons are related to the quantity of ice used to cool.

-         To change from Ton to Kwc. KWc= Ton x 3.516

Levels of redundancy:

-         N – is need and meets base requirements with no redundancy.

-         N+1 – is one additional unit/path/Module more than the base requirement.

-         2N – is two complete units/paths/modules of every one required for the system base.

-         2(N+1) – Two complete (N+1) units/module/paths if there is any failure of one system still leaves and entire stem still working.

Criticality Classification:           

-         N = Single path “No Redundancy”

-         N+1 = Single path with some redundancy

-         2N = Concurrently maintainable

-         2(N+1) = Concurrently maintainable with full fault tolerant-         

Availability rating:

99%                 annual time unavailable = 88 hours

99.9%             annual time unavailable = 8.8 hours

99.99%           annual time unavailable = 53 Minutes

99.999%         annual time unavailable = 5.3 minutes

99.9999%       annual time unavailable = 32 seconds

Uptime Institute Tier IV is 99.995% or 26 minutes/year

Metrics.

            The main power efficiency metrics currently in use within the dc industry are based on the “ratio of IT load to Facilities load”

-         This is referred to as the facility efficiency.

-         Two commonly used metrics are PUE & DCiE

Data center infrastructure efficiency

DCiE = (IT load) /  (Total facility load) x 100%

Power Usage Effectiveness

            PUE = (Total facility load) / (IT load)

What is the IT load?

            This relate to the power consumption of all of the IT equipment within the data center.

What is the facility load?

            This related to the mechanical and electrical systems that support the IT electrical and such as cooling systems (Chiller plant, fans, pumps) air conditioning units, UPS, PDUs etc.

PUE Version 2 has 4 Categories:

            PUE0 =This is still power (KW), but uses case measurements (highest peak measured)

            PUE1 =This is annualized energy measured at the output of the UPS (Lowest accuracy).

            PUE2 =This is annualized energy at the output of the PDU (better accuracy)

            PUE3 =This is annualized energy at the rack/input of IT equipment (best accuracy) 

Future metrics

CUE : Carbon usage effectiveness (Green Grid)

WUE : Water usage effectiveness (Green Grid)

CADE : Carbon average data center efficiency (Uptime inst.)

DPpE : Data Center performance per energy (Green IT promotion Council)