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Publication date: 10-June-2022
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CRUR®
Computer Room Utilization Ratio
CRUR® - COMPUTER ROOM UTILIZATION RATIO
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CRUR® - COMPUTER ROOM UTILIZATION RATIO
1. Foreword
Data centers are now, more than ever, under pressure to ensure that they are optimized and
utilized to its maximum effectiveness and efficiency.
Various metrics have been developed over time looking at optimizing the supporting
facilities such as the power and cooling infrastructure. Metrics such as PUE, WUE etc. have
made their inroads in the data center industry years ago and, although often abused as well,
they have helped the industry to create awareness and improvements.
However, it is EPI’s view that, in addition to existing facilities-oriented metrics, the best
savings can be made at the computer room level. The reason is simple in that for every kW
at the computer room floor there will be a multiple of it at the facility entry side.
Furthermore, MTDC’s (Multi Tenanted Data Centers) could end up being penalized due to
oversubscribed, and underutilized, computer room utilization factors as they would have an
impact on achieving the MTDC’s overall PUE, WUE and other energy efficiency factors.
In certain countries these requirements are mandated by law and it is anticipated that more
countries will follow and adopt similar regulations.
To address this issue, EPI has developed a new metric, CRUR (Computer Room Utilization
Ratio), which data center owners, operators and end-users can immediately use to optimize
the computer room. In addition, it can be applied for trend analysis which could positively
impact the design criteria for future, to be build data centers, resulting in better efficiency,
utilization and return on investment of those data center projects. CRUR is the first ever
metric designed to measure and optimize the core of many data center efficiency issues
which is the computer room itself. It is clear that CRUR, together with metrics such as PUE,
will create a positive impact on the environmental, increasing its sustainability.
This document provides clarity and guidance on the CRUR metric and how to apply it.
This document is a living document and as such, revisions will occur over time to further
enhance this document and the CRUR metric based on data center owners, operators and
service providers’ feedback as well as new trends, technologies, methodologies and other
influencing factors to this metric.
We always welcome industry feedback. Please provide us your feedback and ideas for
improvement via email at support@epi-ap.com
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The other issue in the industry is that there tends to be a habit of overdesigning and
underutilization, causing great wastage of valuable resources as well as creating negative
impact on expected investment returns.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
2. Disclaimer and limitation of liability
The document to which this Notice is an integral part of (the “Document”) has been prepared
by EPI and other subject matter experts. The use or practice of contents of this Document
may involve the use of intellectual property rights (“IPR”), including pending or issued
patents, or copyrights, owned by one or more parties. EPI makes no search or investigation
for IPR. When IPR consisting of patents and published pending patent applications are
claimed and called to EPI’s attention, a statement from the holder thereof is requested, and
EPI will take appropriate action to investigate the claim and subsequent action to ensure
that “IPR” of the respected holder is protected. As such EPI reserves the right to modify this
Document at any time should the need arise to protect the relevant “IPR”.
This Standard does not attempt to address all regulatory requirements. It is the responsibility
of the data center operator to investigate and comply with applicable rules and laws.
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WITHOUT LIMITATION, ANY AND ALL WARRANTIES CONCERNING THE
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WOULD NOT BE PUBLISHED BY EPI WITHOUT SUCH LIMITATIONS.
** Note: The names of the standards listed are protected by copyright laws and are used in
this standard for reference only.
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EPI is the certificate issuing body for the CRUR®. Only accredited CRUR® auditors are
allowed to make claims for conformity to the standard based on the audit principles laid
down in the EPI – Auditor Agreement. A list of valid EPI Certified Auditors can be found
at the EPI website (www.epi-ap.com). While efforts are made to keep this list of certified
auditors current some delay in posting is possible. The authenticity of any auditor can be
verified by writing support@epi-ap.com.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
1.
Foreword .................................................................................................................3
2.
Disclaimer and limitation of liability .....................................................................4
3.
Table of Contents ....................................................................................................5
4.
Scope and application of the CRUR metric ..........................................................6
5.
Normative References ............................................................................................7
6.
Definitions of Terms, Acronyms, Abbreviations and Units of Measure ............8
7.
Introduction to CRUR ..........................................................................................10
8.
8.1
8.2
Facilities: Power Capacity ....................................................................................12
SPCR: Stranded Power Capacity Ratio ....................................................... 12
PCUR: Power Capacity Utilization Ratio ................................................... 13
9.1
9.2
Facilities: Mechanical (Cooling) Utilization .......................................................14
MPUR: Mechanical vs Power Utilization Ratio ......................................... 14
MCUR: Mechanical Capacity Utilization Ratio ......................................... 14
10.1
Facilities: Physical Space .....................................................................................16
RUUR: Rack Unit Utilization Ratio ........................................................ 16
9.
10.
11.
ICT: Data Storage .................................................................................................17
11.1
DSUR: Data Storage Utilization Ratio .................................................... 17
12.
12.1
ICT: Compute Power............................................................................................18
CPUR: Compute Power Utilization Ratio ............................................... 18
13.
ICT: Memory ........................................................................................................19
13.1
MUR: Memory Utilization Ratio ............................................................. 19
14.
ICT: Network ........................................................................................................20
14.1
NPUR: Network Port Usage Ratio .......................................................... 20
14.2
NBUR: Network Bandwidth Utilization Ratio ........................................ 20
15.
CRUR: Calculation Models .................................................................................22
Weight factors .......................................................................................... 22
CRUR calculation models........................................................................ 22
CRURF calculation................................................................................... 23
CRURIT calculation.................................................................................. 23
CRURFIT calculation ................................................................................ 23
15.1
15.2
15.3
15.4
15.5
16.
Monitoring & Reporting Tools ............................................................................24
17.
Self-declaration, Audit and Certification.............................................................25
18.
Appendix-A: Tips .................................................................................................26
18.1
CPU utilization......................................................................................... 26
18.2
Network device power consumption ....................................................... 26
18.3
UPS Distributed Redundant / Catcher system configuration ................... 27
19.
Copyright ...............................................................................................................29
20.
EPI: Company Profile...........................................................................................30
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3. Table of Contents
CRUR® - COMPUTER ROOM UTILIZATION RATIO
4. Scope and application of the CRUR metric
The scope of the CRUR metric is the computer room and its direct supporting electrical
(power) and mechanical (cooling) infrastructure as well as the ICT infrastructure.
The CRUR metric can be applied to either the facilities only, ICT only or the combination.
The notation of the CRUR will indicate what is under the scope;
CRURF
CRURIT
CRURFIT
: Computer Room Utilization Ratio for Facilities components only
: Computer Room Utilization Ratio for IT components only
: Computer Room Utilization Ratio for IT & Facilities components
As mentioned, it is imperative for the CRUR metric to always include the scope notation to
avoid incorrect and/or misleading information.
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The organization can choose either one, or all, of the metrics depending on the business
requirements and scope of control. For example, an Enterprise Data Center might prefer to
implement CRURFIT as it has full control over both the data center facilities as well as the
ICT infrastructure whereas a commercial data center operator might prefer to only
implement CRURF as they (might) have very little or no control over the ICT equipment
deployed by their customers. Cloud providers may consider using the CRURFIT as they often
have full control over both the facilities and ICT equipment.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
5. Normative References
ASHRAE
ANSI/TIA-942
BREEAM
EN 50600
EU CoC
ISA-71.04.2013
ISO 14001
ISO 22237
ISO 30134
ISO 50001
IPMVP
LEED
NABERS
SS564
ITU-T L.1300
ITU-T L.1310
ETSI ES 203 136
V1.1.1 (2013-05)
ETSI EN 303 470
V1.1.1
ETSI EN 303 215
V1.3.1
ETSI TS 105 1742 V1.3.1
American Society of Heating, Refrigerating and Air-Conditioning
Engineers
Telecommunication Infrastructure Standard for Data Centers
Building Research Establishment Environmental Assessment
Method
Information technology - Data centre facilities and infrastructures
European Union Code of Conduct
Environmental Conditions for Process Measurement and Control
Systems
Environmental management systems
Information technology - Data centre facilities and infrastructures
Data Centers – Key Performance Indicators
Energy Management System (EnMS)
International Performance Measurement and Verification Protocol
Leadership in Energy and Environmental Design
National Australian Built Environment Rating System
Sustainable data centers – Energy and environmental management
systems
Best practices for green data centres
Energy efficiency metrics and measurement methods for
telecommunication equipment
Environmental Engineering (EE); Measurement methods for
energy efficiency of router and switch equipment
Energy Efficiency measurement methodology and metrics for
servers
Measurement methods and limits for power consumption in
broadband telecommunication networks equipment
Part 2: ICT Sites: Implementation of energy and lifecycle
management practices
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Use the following documents as additional reference sources for this Standard. Please note
that all standards are ‘living’ documents. Care should be taken to always apply the ‘current’
version of the standard.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
6. Definitions of Terms, Acronyms, Abbreviations and Units of Measure
Term
Definition
AC
Benchmark
Air Conditioner
A standard or point of reference against which things may be
compared.
Building Management/Monitoring System
Officially recognize (someone or something) as possessing certain
qualifications or meeting certain standards.
Cubic Feet per Minute / Cubic Meter per Hour
Configuration Management System
Computerized Maintenance Management System
Carbon Usage Effectiveness
Central Processing Unit
Computer Room Air-conditioner
To adhere to an act or its regulations
To meet a requirement, standard, or procedure
The room containing continuous operation for ICT equipment
which processes and stores business processes and data
Any individual or organization which uses the services provided by
the organization
The computer room plus all its supporting facilities
Energy Efficiency Ratio of equipment
Environmental Monitoring System
Energy Management System
End Of Life
End Of Service
A break or other defect in a system and/or equipment.
A basic structure underlying a system and/or concept.
Gigabyte
Gigabits per second
Heating, Ventilation and Air-conditioning
High Voltage/High Tension
Information and Communications Technology
Key Performance Indicator
Megabyte
Megabits per second
Massive Array of Idle Disks
Maintenance Operation Procedure
A contract that defines how various departments within the data
center organization plan to deliver a service or set of services to
support an SLA.
The data center service provider.
Power Distribution Unit
Set of rules and guiding principles that shall be adhered to, while
executing related process(es) and procedure(s).
A set of specific steps that describe how an activity should be
carried out, and by whom.
A set of interrelated activities that delivers a desired outcome.
Power Usage Effectiveness
At least once a year or after every major change
An area or room which requires additional security measures to
ensure risk of disturbance to this room or area is minimized. For the
definition of this standard, it includes (but is not limited to);
BMS
Certified
CFM/CMH
CMS
CMMS
CUE
CPU
CRAC
Compliance
Conformity
Computer room
Customer
Data center
EER
EMS
EnMS
EOL
EOS
Fault
Framework
GB
Gbps
HVAC
HV/HT
ICT
KPI
MB
Mbps
MAID
MOP
Operational Level Agreement
Organization (the)
PDU
Policies
Procedure
Process
PUE
Regular
Restricted area
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The following table describes some of the terminology used in this standard.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
REF
ROI
Service Improvement Process
(SIP)
SHR
SLA – Service Level Agreement
Standard
Supporting facilities
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TB
UPS
WAN
WUE
Transformer room/area, Generator room/area, UPS room,
Computer room etc.
Renewable Energy Factor
Return on Investment
A service expansion/improvement process that builds on the
existing services and identifies opportunities to improve and/or add
new services.
Sensible Heat Ratio
A contract between a service provider (either internal or external)
and the end user that defines the level of service expected from the
service provider.
A document that provides requirements, specifications, guidelines
or characteristics that can be used consistently to ensure that
materials, products, processes and services are fit for their purpose.
The technical and operational areas required to support the
computer room environment such as UPS room, Generator
area/room, Network Operations Center (NOC) etc.
Terabyte
Uninterruptable Power Supply
Wide Area Network
Water Usage Effectiveness
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CRUR® - COMPUTER ROOM UTILIZATION RATIO
7. Introduction to CRUR
The computer room is at the heart of every data center. The aim of any business is to ensure
that the design is based on business requirements which includes today’s, as well as future
requirements.
This, and other factors, has led to many business and data center designers to “play safe” by
doing a fair amount of oversizing with the “thinking” that it is better to have 100kW too
much than 1kW too little resulting in a level of “waste”. Not only due to unused space,
power etc. but also financial waste due to overspending which immediately negatively
affects the ROI. This has also an impact on the environment as often underutilized data
centers result in more in-efficient data center environments. Ideally, we could predict the
future knowing exactly what we need to have 5, 10, 15 or even 20 years from now. However,
this is simply impossible.
The other issue is that in MTDC’s (Multi Tenanted Data Centers), the underutilization/
oversubscription on services could create issues for the data center operator as the
underutilization/oversubscription of its tenants could have a (major) impact on the overall
efficiency the MTDC can achieve. For example, if the data center operator assumed at least
80% load in the building which would then achieve the required PUE, the operator could
possibly end up in great financial and legal trouble if the tenants do not create the loading
factors for which they signed up.
There is clearly a need to measure computer room utilization. However, the sad news is that
many organizations don’t measure computer room waste as a way to optimize it and
therefore not only create a better ROI but also to optimize it such that the data center has
less impact on the environment. It is clear that a metric is required so that data center
operators and owners gain insight in how much over dimensioning has taken place and how
to make sure that rightsizing and optimization is achieved in the best possible way.
To optimize the computer room, we need to review the design capacity and used capacity
of the following components;
Facilities components
- Power capacity
- Cooling capacity
- Physical space
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The ‘future requirements’ part is often at the heart of the problem when it comes the sizing
the computer room as it is very difficult, if not impossible, to predict the future. This is not
only difficult to predict due to unknown business climate and outlook of the future, but also
due to technology changes that might happen including those unknown to anyone at this
moment in time. One should not forget that data centres are often expected to have a lifespan
of 10-20 years and more and with such a long lifespan it is virtually impossible to make any
accurate long-term predictions.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
ICT components
- Data storage capacity
- Compute power
- Memory capacity
- Network ports and bandwidth
There are still several data centers who lack in the ability to centrally monitor resources
usage such as detailed power consumption monitoring or CPU/memory utilization etc.
Obviously, it is very important to install monitoring systems as CRUR analysis will be
difficult, if not impossible, in a manual fashion. Section 16 of this document will discuss
monitoring systems.
Suffice to say that any usage and optimization should ensure that data integrity, availability
and security should not be compromised to the point that Service Level Agreements might
be at risk of being violated.
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The next few sections will provide an explanation on each of the metrics within the overall
CRUR metric and how to calculate them. Section 15 will provide guidance on how to
calculate CRURF , CRURIT and CRURFIT.
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CRUR® - COMPUTER ROOM UTILIZATION RATIO
8. Facilities: Power Capacity
Power capacity utilization, which is directly related to the computer room, has a number of
measure points. These include, but are not limited to;
• UPS
• PDU
• Busbar
• Rack
• Rack density
Whilst 100% utilization on all these points would be the theoretical desirable point, in
practice capacity utilization is often capped at 80 or 90% depending on the load and diversity
factors and the risk appetite of the organization.
When understanding the power utilization, consideration should be given to the power
infrastructure layout. For example, where the computer room is using an A & B power
distribution configuration to allow for failover, we should consider that a 40/45% load
condition on A and B feed could be considered the optimum utilization under normal
operational mode. This to ensure that we can transfer the load from one feed to the other
feed resulting in the surviving feed to then have 80/90% load. This will allow for a safe and
uninterrupted operation of the computer room.
The optimized load condition percentage on a single feed will be more difficult to establish
in a power distribution where a catcher system principle has been deployed. A catcher
system could be as simple as having an A and B feed with a single catcher system catering
for either the A or B feed or it could be much more complex where multiple active
distribution paths are supported by one or multiple catcher systems.
When using a catcher system setup, it will be important to calculate the optimized power
capacity ratio and apply that to benchmark the current ratio.
8.1 SPCR: Stranded Power Capacity Ratio
Redundant power infrastructure often leads to stranded capacity. It is therefore important to
factor in stranded capacity to drive for a more efficient data center setup.
The SPCR metric can be calculated by the following formula;
𝑆𝑃𝐢𝑅 =
𝑁 − πΆπ‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ (∗)
π‘‡π‘œπ‘‘π‘Žπ‘™ π‘ˆπ‘ƒπ‘† π‘π‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ π‘–π‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘(∗∗)
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Furthermore, measuring utilization at this level of granularity would introduce a higher level
of complexity which defeats the purpose of the CRUR metric which is aimed at being easy
to use and providing a high-level insight into the computer room utilization overall.
However, if an organization wishes to go into greater level of detailed analysis of the design
optimization, now or for future data centers, then this could of course be applied.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
Note-*: N Capacity is the maximum base capacity designed for the ICT load in kW.
Example-1
Example-2
N-Capacity = 100kW
Total UPS Capacity = 200kW
SPCR = 100/200 = 0.5
N-Capacity = 200kW
Total UPS Capacity = 300kW
SPCR = 200/300 = 0.66
8.2 PCUR: Power Capacity Utilization Ratio
The power capacity installed vs. current power capacity (currently) in use indicates the
effective sizing of electrical equipment power capacity vs. the actual current power load for
the ICT equipment inside the computer room. Too much over capacity installed vs. ICT
power load in use leads to in-efficiencies and consideration should be given to reduce the
active (UPS) power capacity or to potentially consider rotating schedules etc.
It should be noted that growth strategies play an important role for this metric. However,
much can be done by having an appropriate capacity growth strategy i.e. full build out vs. a
phased build out.
The PCUR metric can be calculated by the following formula;
π‘ƒπΆπ‘ˆπ‘… =
π‘‡π‘œπ‘‘π‘Žπ‘™ 𝐼𝐢𝑇 π‘™π‘œπ‘Žπ‘‘(∗)
π‘‡π‘œπ‘‘π‘Žπ‘™ π‘ˆπ‘ƒπ‘† π‘π‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ π‘–π‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘(∗∗)
Note-*: Total ICT load is based on all current load in the computer room measured in kW.
Where loads vary by more than 15% the average kW load over a 7 consecutive day period
should be used.
Note-**: Total UPS capacity installed is the total UPS capacity installed (in kW) minus
redundancy in parallel or catcher designs. However, total UPS capacity does include all
UPS capacity including rackmount UPS systems which might be installed in addition to the
centralized UPS system(s) in a serial power train configuration.
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Note-**: Total UPS capacity installed is the total UPS capacity installed (in kW) including
all UPS capacity including rackmount UPS systems which might be installed in addition to
the centralized UPS system(s) in a serial power train configuration.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
9. Facilities: Mechanical (Cooling) Utilization
Cooling capacity utilization has two important aspects;
• Total mechanical (cooling/AC) capacity installed vs. total electrical power
capacity installed
• Total cooling mechanical (cooling/AC) capacity installed vs. current cooling
capacity required
9.1 MPUR: Mechanical vs Power Utilization Ratio
The cooling capacity installed vs. the power capacity installed will indicate how much
oversizing has been done on the mechanical infrastructure compared to the maximum
power, and therefore heat, dissipation in the room. This kind of oversizing is often done to
cater for cooling in-efficiencies expected in the room as theoretically we only need 1kW of
(sensible) cooling capacity for every 1kW of ICT heat load. Oversizing has an impact on
both ROI as well as daily efficiency of the data center.
π‘€π‘ƒπ‘ˆπ‘… =
π‘‡π‘œπ‘‘π‘Žπ‘™ π‘ˆπ‘ƒπ‘† π‘π‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ π‘–π‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘(∗)
π‘‡π‘œπ‘‘π‘Žπ‘™ 𝐴𝐢 π‘π‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ π‘–π‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘(∗∗)
Note-*: Total UPS capacity installed is the total UPS capacity installed minus all
redundancy. For example, if there are two feeds with each a 100kW UPS systems and they
are designed to cater for CM – Concurrent Maintainability or FT – Fault Tolerance
considerations, then only the single capacity must be used in this formula. In this example
one would use 100kW instead of the total purchased 200kW.
Note-**: Total capacity is determined by adding the total cooling capacity (in kW/SHR) of
all installed mechanical equipment installed minus additional units for redundancy purpose
if these units are not running. If additional units are running as part of the total cooling
capacity pool, then these additional units need to be added to the total cooling capacity
installed.
9.2 MCUR: Mechanical Capacity Utilization Ratio
The cooling capacity installed vs. current cooling capacity (currently) required indicates the
effective sizing of mechanical equipment vs. the actual current heat load. Too much over
capacity in use vs. current heat load leads to in-efficiencies and consideration should be
given to reduce the active cooling capacity by considering rotating schedules etc.
It should be noted that growth strategies play an important role for this metric. However,
much can be done by having an appropriate capacity growth strategy i.e. full build out vs.
phased build out.
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The MPUR metric can be calculated by the following formula;
CRUR® - COMPUTER ROOM UTILIZATION RATIO
The MCUR metric can be calculated by the following formula;
π‘€πΆπ‘ˆπ‘… =
π‘‡π‘œπ‘‘π‘Žπ‘™ 𝐼𝐢𝑇 π‘™π‘œπ‘Žπ‘‘(∗)
π‘‡π‘œπ‘‘π‘Žπ‘™ 𝐴𝐢 π‘π‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ π‘–π‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘(∗∗)
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Note-*: Total ICT load is based on all current load in the computer room measured in kW.
Where loads vary by more than 15% the average kW load over a 7 consecutive day period
should be used.
Note-**: Total AC capacity installed is the total AC capacity installed (in kW/SHR) minus
all redundancy unless the redundant units are actively running.
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CRUR® - COMPUTER ROOM UTILIZATION RATIO
10. Facilities: Physical Space
The physical space for a computer room should be utilized effectively as real estate
cost is often high. Assuming a rack-based setup, there could be a variety of factors
influencing the number of racks which can be installed within a computer room.
Such factors include;
• The width and depth of the racks
• Aisle width taking into consideration power density, work/maintenance space
requirements, regulatory safety requirements
• Cooling system setup e.g. perimeter/in-row etc.
As the basis of usable space within the computer room the space within the rack
itself is applied. This is expressed in RU – Rack Unit which is commonly
abbreviated to U. One U is 1.75inch / 44.45mm.
10.1 RUUR: Rack Unit Utilization Ratio
The rack unit utilization is calculated by using the following formula
π‘…π‘ˆπ‘ˆπ‘… =
π‘…π‘Žπ‘π‘˜ π‘ˆπ‘›π‘–π‘‘ πΏπ‘œπ‘π‘Žπ‘‘π‘–π‘œπ‘›π‘  π‘ˆπ‘ π‘’π‘‘
π‘…π‘Žπ‘π‘˜ π‘ˆπ‘›π‘–π‘‘ πΏπ‘œπ‘π‘Žπ‘‘π‘–π‘œπ‘›π‘  πΌπ‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘(∗)
Note*:
- When having varying rack heights, multiply the number of each rack type with the
available U for that rack type e.g. (16 Racks x 42U) + (18 Racks x 48U) = 1,536
-
When deploying ToR type of network infrastructure, do count all U space in the rack
including the U which is occupied by the network switch(es)
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On the basis of keeping the metric simple, the following assumptions apply;
• Computer rooms are most likely being populated with standard racks
(width, depth and height might vary)
• Computer rooms comply to local (fire) safety and safe workplace
regulations
• Computer rooms are most likely to be fully populated with racks
CRUR® - COMPUTER ROOM UTILIZATION RATIO
11. ICT: Data Storage
Data storage is a component where it is impossible to determine the design capacity for a
computer room. Data storage capacity requirements are dynamic to the business
(applications) and as such, capacity could easily, and most likely, change frequently over
time. Technology advances in the future will also have a major impact on the total amount
of data storage capacity available within a given space whether that is a computer room, a
rack or even a server/storage unit. However, one objective is clear, it is important to right
size it as best as possible at any given time to avoid underutilization and therefore over
investment especially knowing that the price for storage often (dramatically) reduce e.g. the
GB/USD of today is most likely much higher than that of the GB/USD one year later. It is
for this reason that for this component of the computer room we only measure currently
installed capacity vs currently used capacity.
It is therefore required to create logical data storage pools. This will allow the organization
to determine the overall utilization ration as well as “departmental/application specific”
ratios.
11.1 DSUR: Data Storage Utilization Ratio
The data storage utilization ratio is calculated by comparing the used vs. installed data
storage for every logical storage pool and then average out. The formula for calculating each
data storage pool is:
π·π‘†π‘ƒπ‘œπ‘œπ‘™1 =
π·π‘†π‘ƒπ‘œπ‘œπ‘™1 π‘ˆπ‘ π‘’π‘‘
π·π‘†π‘ƒπ‘œπ‘œπ‘™1 πΌπ‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘
After calculating each individual Data Storage Pool utilization, we can calculate the total
by using the formula below;
π·π‘†π‘ˆπ‘… =
π·π‘†π‘ƒπ‘œπ‘œπ‘™1 + π·π‘†π‘ƒπ‘œπ‘œπ‘™2 + π·π‘†π‘ƒπ‘œπ‘œπ‘™ 𝐸𝑇𝐢
𝑋
X = Total number of data storage pools.
Note; Pls ensure that one unit of measure is used e.g. MB, GB, TB for all Data Storage
Pools.
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Consideration should be given to the fact that data storage cannot always be considered as
one big data storage pool which dynamically can be shared amongst a variety of applications
and business units within an organization e.g. the storage pool available for the human
resource department is most likely (physically) separated from the online transaction
processing application for various reasons such as performance, security etc.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
12. ICT: Compute Power
As with data storage, compute power is also a component where it is impossible to predict
the required design capacity for a computer room over its full lifespan.
Many compute power benchmarks have been established over time. Some are based on total
system performance such as FLOPS (Floating-Point Operations Per Second) or MIPS
(Million Instructions Per Second) and other variations thereof whereby the applied choice
and usage typically varies depending on what favours the architecture of the vendor. Other
measure of compute power use metrics such as the clock-speed as a single parameter or in
combination with bus-width etc.
CRUR takes a very simple approach in that it does not try to establish a new or single
benchmark number based on parameters as indicated above. CRUR takes the simple
approach that a CPU runs at a maximum of 100% process load. Anything less than 100%
theoretically means the CPU is not utilized to its full capacity.
We also need to consider that CPUs typically run at varying load conditions at any given
time and as such we should measure the CPU utilization over a period. Time recorded for
determining the average load condition should not be less than 7 consecutive days.
A final consideration is that not every server will run at its most optimum energy utilization
rate when running under high load. As such one could consider setting the optimum
threshold at a lower level where desired.
12.1 CPUR: Compute Power Utilization Ratio
The compute power utilization ratio is calculated by calculating the average CPU load
measured over a 7-day consecutive period. Where feasible, it would be desirable to consider
CPU load per logic CPU pool allocated for a defined scope such as an
application/application group or business group. The formula for calculating the CPU load
pool is:
πΆπ‘ƒπ‘ˆπ‘…π‘ƒπ‘œπ‘œπ‘™1 =
πΆπ‘ƒπ‘ˆπ‘ƒπ‘œπ‘œπ‘™1 πΏπ‘œπ‘Žπ‘‘ %
100%
After calculating each individual CPU Power Pool utilization, we can calculate the total by
using the below formula;
πΆπ‘ƒπ‘ˆπ‘… =
πΆπ‘ƒπ‘ˆπ‘…π‘ƒπ‘œπ‘œπ‘™1 + πΆπ‘ƒπ‘ˆπ‘…π‘ƒπ‘œπ‘œπ‘™2 + πΆπ‘ƒπ‘ˆπ‘…π‘ƒπ‘œπ‘œπ‘™ 𝐸𝑇𝐢
𝑋
X = Total number of compute power pools.
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However, we need to consider other factors such as that no data center wants to have all its
CPUs running at 100% load all the time as then there would be no room for (temporary)
increased workload requirements.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
13. ICT: Memory
Memory utilization has similar properties as compute power. The memory pool is tied to
the CPU pool meaning that memory has a direct relation to the CPU (or CPUs) driving them.
As such, the memory pool definitions will be in a one-to-one relation to compute power
pool definitions. Memory capacity will often change depending on application requirements
by simply adding or removing memory modules. It is therefore that the memory utilization
will also be measured as a relation between installed and used.
We also need to consider that memory utilization typically varies at any given time and as
such we should measure the memory utilization over a period. Time recorded for
determining the average load condition should not be less than 7 consecutive days.
13.1 MUR: Memory Utilization Ratio
π‘€π‘ƒπ‘œπ‘œπ‘™1 =
π‘€π‘ƒπ‘œπ‘œπ‘™1 π‘ˆπ‘ π‘’π‘‘
π‘€π‘ƒπ‘œπ‘œπ‘™1 πΌπ‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘
After calculating each individual memory pool, we can calculate the total by using the
formula below;
π‘€π‘ˆπ‘… =
π‘€π‘ƒπ‘œπ‘œπ‘™1 + π‘€π‘ƒπ‘œπ‘œπ‘™2 + π‘€π‘ƒπ‘œπ‘œπ‘™ 𝐸𝑇𝐢
𝑋
X = Total number of memory pools.
Note; Pls ensure that one unit of measure is used e.g. MB, GB, TB for all Memory Pools.
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The memory utilization ratio is calculated by calculating the used vs. installed memory for
every memory pool. The formula is:
CRUR® - COMPUTER ROOM UTILIZATION RATIO
14. ICT: Network
Network utilization has two primary components;
• Number of ports installed vs. used
• Bandwidth available vs. used
The number of ports and their utilization is relatively simple to establish by counting the
number of ports vs. active ports.
Measuring bandwidth utilization is potentially more complicated as there can be various
points to measure utilization such as network utilization within the computer room itself as
well as connectivity of the total data center building to the outside world. For example,
whilst data analytics applications might rely more on network bandwidth within the
computer room itself, video streaming applications require appropriate bandwidth to the
outside world.
The network port used ratio is calculated by calculating the used vs. installed network ports
within the computer room. The formula is:
π‘π‘ƒπ‘ˆπ‘… =
π‘π‘’π‘‘π‘€π‘œπ‘Ÿπ‘˜ π‘ƒπ‘œπ‘Ÿπ‘‘π‘  π‘ˆπ‘ π‘’π‘‘(∗)
π‘π‘’π‘‘π‘€π‘œπ‘Ÿπ‘˜ π‘ƒπ‘œπ‘Ÿπ‘‘π‘  πΌπ‘›π‘ π‘‘π‘Žπ‘™π‘™π‘’π‘‘
Note(*); This term refers to the total number of ports on all the network switches (across
all the line cards) that are active (with cables plugged in). The remaining ports
on the switch should explicitly be disabled using the switch’s command line
interface.
Consideration should be given to setting limits to the line rate forwarding capacity of
individual ports (typically, the capacity of a full-duplex 1 Gbps port can also be set to 10
Mbps and 100 Mbps) to limit the power usage of each port in relation to the capacity
required.
14.2 NBUR: Network Bandwidth Utilization Ratio
The network bandwidth utilization ratio, for the purpose of CRUR, is measured at the
individual computer room level under the scope of the CRUR metric application. The
capacity installed vs. used is related to the network going into the computer room under
scope which is typically the capacity going into the MDA – Main Distribution Area.
π‘π΅π‘ˆπ‘… =
π‘ˆπ‘ π‘’π‘‘ π΅π‘Žπ‘›π‘‘π‘€π‘–π‘‘π‘‘β„Ž (𝐺𝑏𝑝𝑠)
π΅π‘Žπ‘›π‘‘π‘€π‘–π‘‘π‘‘β„Ž πΆπ‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦ (𝐺𝑏𝑝𝑠)
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14.1 NPUR: Network Port Usage Ratio
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We also need to consider that network bandwidth utilization typically varies at any given
time and as such we should measure the bandwidth utilization over a period. Time recorded
for determining the average load condition should not be less than 7 consecutive days.
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15. CRUR: Calculation Models
Each of the ratios detailed in this document serve a certain purpose to assess the current
utilization ratios in various components of a computer room and its direct supporting
facilities infrastructure.
It should be noted that certain utilization ratios achieved might be far from what could be
considered to be the optimum. However, utilization ratios should take into account business
factors such as the current state of the business and expected growth over a defined period
of time. Hence, a low ratio does not necessarily indicate a poorly designed and/or used data
center, it might have been over designed for the purpose of catering for future growth. The
CRUR can then be used as a metric to keep track on planned growth and planned
optimization targets for the years to come versus targets achieved.
15.1 Weight factors
The CRUR metric does not have weight factors for the various sub-metrics such as CPUR,
CMUR etc. First of all, weight factors are subjective. Secondly, they could vary from data
center type and industry. Thirdly, weight factors could vary depending on the business
objective. Therefore, having a fixed set of weight factors would not make sense.
If we would allow the data center operator/owner to set their own weight factors based on
business objectives, then the risk is that those weight factors might also be abused by a select
few who want to boost the overall CRUR ratio for business/marketing purposes. This would
not be in the best interest for the industry.
Therefore, weight factors should not be applied as any improvement in any of the categories
would automatically result in an overall improvement in the CRUR ration. Of course, as a
data center operator owner, one can always select which of the sub-metric(s) is/are more
important and deserves more attention for improvement programs.
15.2 CRUR calculation models
As explained in the introduction, there are three types of CRUR being;
CRURF
CRURIT
CRURFIT
: Computer Room Utilization Ratio for Facilities components only
: Computer Room Utilization Ratio for IT components only
: Computer Room Utilization Ratio for IT & Facilities components
It is compulsory for those using the CRUR metric to display which of the three is being used
by having the subscript indicator.
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By keeping track of the CRUR, the organization can take lessons learned on how CRUR
changes over time to understand whether a too aggressive oversizing model was used often
leading to an impact to the overall ROI.
CRUR® - COMPUTER ROOM UTILIZATION RATIO
15.3 CRURF calculation
The CRURF is calculated by applying the following formula;
πΆπ‘…π‘ˆπ‘…πΉ =
CRURF
SPCR
PCUR
MPUR
MCUR
RUUR
𝑆𝑃𝐢𝑅+ π‘ƒπΆπ‘ˆπ‘…+ π‘€π‘ƒπ‘ˆπ‘… + π‘€πΆπ‘ˆπ‘… + π‘…π‘ˆπ‘ˆπ‘…
5
: Computer Room Utilization Ratio - Facilities
: Stranded Power Capacity Ratio
: Power Capacity Utilization Ratio
: Mechanical vs Power Utilization Ratio
: Mechanical Capacity Utilization Ratio
: Rack Unit Utilization Ratio
15.4 CRURIT calculation
πΆπ‘…π‘ˆπ‘…πΌπ‘‡ =
CRURIT
DUSR
CPUR
MUR
NPUR
NBUR
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The CRURIT is calculated by applying the following formula;
π·π‘†π‘ˆπ‘… + πΆπ‘ƒπ‘ˆπ‘… + π‘€π‘ˆπ‘… + π‘π‘ƒπ‘ˆπ‘… + π‘π΅π‘ˆπ‘…
5
: Computer Room Utilization Ratio - IT
: Data Storage Utilization Ratio
: Compute Power Utilization Ratio
: Memory Utilization Ratio
: Network Port Usage Ratio
: Network Bandwidth Utilization Ratio
15.5 CRURFIT calculation
The CRURFIT is calculated by applying the following formula;
πΆπ‘…π‘ˆπ‘…πΉπΌπ‘‡ =
CRURFIT
CRURIT
CRURF
πΆπ‘…π‘ˆπ‘…πΉ + πΆπ‘…π‘ˆπ‘…πΌπ‘‡
2
: Computer Room Utilization Ratio – IT & Facilities
: Computer Room Utilization Ratio - IT
: Computer Room Utilization Ratio - Facilities
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16. Monitoring & Reporting Tools
It is highly recommended to automate the measurement and reporting on the CRUR metric
and sub-metrics. There are a wide variety of data center monitoring tools which can support
part or all the measurements and provide an automated view on the CRUR metric.
Whilst such automation could be of great value, careful evaluation must take place that the
measurement locations, calculation formulas as well as measurement evaluation intervals
are correctly defined to provide a reliable metric reporting.
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An audit and certification of the data center for CRUR will include the evaluation of the
implementation of the monitoring and reporting tools used by the data center to ensure an
accurate and reliable reporting on CRUR.
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17. Self-declaration, Audit and Certification
Organizations are free to use the CRUR metric and indicate the CRUR values as long as
they clearly indicate the area under scope and that the value is based on self-declaration.
EPI, and its authorized partners, can provide official audit and certification services for
CRUR. This will provide the additional level of trust to the customers of the data center that
the measurements and calculation have been audited by trained professionals. This 3rd party
declaration will ensure that customers know that an independent and impartial review has
taken place providing an accurate representation of the values of CRUR.
This can of course also used by the data center operator/owner as values for which
approvement plans can be established to optimize the data center.
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Please contact EPI at sales@epi-ap.com for further information.
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18. Appendix-A: Tips
The aim of the CRUR metric is to have a relatively simple way to analyze how well the
computer room is optimized from ‘installed’ vs. ‘used’ perspective. However, a data center
operator/owner could further enhance the analysis at various levels depending on much time
and resources are available.
The data center operator/owner could/should also consider other factors which might impact
the CRUR or optimization plans. The list below gives some guidance on some of the
potential considerations. It is by no means an exhaustive list. EPI is very interested in realworld experiences in computer room optimization and tips so that over time the list below
can be expanded for the benefit of all organizations who like to implement the CRUR
metric.
Theoretically one would consider running a CPU at 100% utilization is the optimum.
However, running CPUs at that level of utilization has a number of potential downsides
such as;
a. Thermal throttling potentially causing the system to shut down
b. Decreased lifespan of ICT hardware
c. Increased demand for cooling which in turn increases the demand for power and
therefore cooling capacity
CPU manufacturers often indicate optimum performance levels balancing CPU
performance vs. power capacity.
18.2 Network device power consumption
There is a vast difference between various network devices and the power they consume.
For example; With no port connectivity, the Netgear JGS524 consumes approximately 20
Watt whereas the Linksys LGS123 consumes only approximately 12 Watt despite both
devices being a 24 ports network device. Please note that these numbers are not indicative
of power consumption efficiency for the whole range of products for these two
manufacturers so care should be taken on product-by-product basis.
It is clear that when selecting network devices it is important to review the actual power
consumption as the network device will be powered on 24x7 and, with many network
devices installed in a computer room environment, the power consumption cost might far
outweigh difference in purchase cost.
Another consideration is to whether deploy unmanaged or managed network devices. In
most organization, especially larger network devices, are fully managed which provides the
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18.1 CPU utilization
CRUR® - COMPUTER ROOM UTILIZATION RATIO
organization with the ability to setup the device based on business requirements. This
includes the activation/de-activation of network ports which are not being used.
Unfortunately, in many computer room environments this feature is not being used for the
reason that its just easier to leave them all on so one can plug in a cable in any port knowing
that it is active. However, consider that a typical active network port with no traffic still
consumes approx. 20-25 Watt vs. a port running at approx. 50% bandwidth to consume
typically 25-40 Watt. With potentially many ports unused, it is clear that good savings can
be made considering that every 1kW of power in the computer room also requires energy
to cool the heat generated. Besides that, unused ports which are being blocked will also not
being ‘abused’ by plugging in a network cable without proper change management
consideration leading to undocumented network changes to which so many organization are
prone.
Most data centers which are designed to Rated-3 or Rated-4 or similar standards or
guidelines, have traditionally been designed around the A and B power feed configuration
providing additional power resiliency. However, that requires that the UPS configuration
for the computer room which has an A and B feed, should not cross more than 45% on each
feed so that during a failover scenario the surviving UPS (cluster) does not carry more than
90% load ensuring the ICT systems can continue to operate without any interruption.
Although UPS technology advancement has resulted in better efficiency even under lower
load conditions, using the traditional A & B setup will also require a large financial
commitment as basically two power infrastructures are being build.
An alternative option is to configure the UPS systems in a distributed redundant or catcher
system configuration. The illustrations below shows the advantage from a sizing point of
view.
Provides only A / B failover.
During maintenance/fault only one
feed will be active.
Provides only A / B failover. During
maintenance/fault of one UPS in a cluster
the other UPS will still be active.
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18.3 UPS Distributed Redundant / Catcher system configuration
Provides only A / B failover. During
maintenance/fault the catcher takes over
the full load. Additional ATS/STS
systems required
Provides only A / B failover. During
maintenance/fault catcher takes over the
full load. Catcher is fed through
maintenance bypass circuit of UPS or
via wrap-around
There are several other factors to consider when deciding on traditional A&B, distributed
redundant or catcher systems, please consult your electrical consultant.
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CRUR® - COMPUTER ROOM UTILIZATION RATIO
CRUR® - COMPUTER ROOM UTILIZATION RATIO
19. Copyright
EPI® (Enterprise Products Integration Pte Ltd) is the Intellectual Property and Trademark
owner of the CRUR metric.
Organizations can use the CRUR metric to analyze and optimize their computer room.
Where the organization declares CRUR value(s) it shall;
- Indicate the appropriate notation to declare what is under the scope of the indicated
CRUR (i.e. CRURF, CRURIT, or CRURFIT)
- Indicate that the CRUR is based on self-declaration
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Only EPI, and its authorized organizations, can audit and certify CRUR.
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20. EPI: Company Profile
EPI® (Enterprise Products Integration Pte. Ltd.) offers an extensive range of data center
services includes services such as, data center consulting, design evaluation, design
validation, surveys, assessments, audits and certification based on standards such as ISO,
ANSI/TIA-942, DCOS© and other relevant international data center standards.
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EPI® also offers a wide range of globally accredited certified data center training programs
such as, CDCP®, CDCS®, CDCE®, CTDC®, CTIA®, CTEA®, CTLA® CDMS®, CDFOM®,
CDFOS® CITO®, CITM®, CITD®, CDESS®, CDRP® and CNCDP® which enable
organizations to educate and align their staff on data center design principles, data center
efficiency, green data center principles, data center management, data center operations
management, security management, disaster recovery management. All courses are
accredited by EXIN®.
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