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Data center tiers by Uptime Institute and TIA. Short overview

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Uptime Institute's Tier Classification System is one of the key-words in the data center industry. Although, there are more talks on it than already certified data centers. What's that? In general, this is widely known as the definition of four levels that describe the availability of data according to the hardware and infrastructure advancement, redundancy and sustainability at a given data center location. The rule is – the higher the tier is given for data center, the greater availability is guaranteed. Therefore, it's good to have a short summary of requirements defined for each level assigned to all four tiers. This can enable us to shortly estimate the answer for the common question – "on which tier are we in fact"? Also, do we have to refer to Uptime Institute only? What about Telecommunications Industry Association (TIA)? Let's take a look and have short reference guidelines.

 

First - Uptime Institute's Tier Classification System via commonly known tables with requirements:

 

Tier I

Tier II

Tier III

Tier IV

Building type

Tenant

Tenant

Stand-alone

Stand-alone

Staffing shifts
Staff/shift

None
None

1 Shift
1/Shift

1 +Shifts
1-2/Shift

"24 by forever"
2+/Shift

Usable for critical load

100% N

100% N

90% N

90% N

Initial build-out kW per cabinet (typical)

<1 kW

1-2 kW

1-2 kW

1-3 kW

Ultimate kW per cabinet (typical)

<1 kW

1-2 kW

>3 kW

>4 kW

Support space to raised-floor ratio

20%

30%

80-90+%

100+%

Raised-floor height (typical)

12 inches

18 inches

30-36 inches

30-42 inches

Floor loading lbs/ft

85

100

150

150+

Utility Voltage (typical)

208, 480

208, 480

12-15 kV

12-15 kV

Single Points-of-Failure (SPOFs)

Many + human error

Many + human error

Some + human error

Fire, EPO + some human error

Representative planned maintenance shut downs

2 annual events at 12thours each

3 events over 2 years at 12 hours each

None required

None required

Representative site failures

6 failures over 5 years

1 failure every year

1 failure every 2.5 year

1 failure every 5 year

Annual site-caused, end-user downtime (based on field data)

28.8 hours

22.0 hours

1.6 hours

0.8 hours

Resulting end-user availability based on site-caused downtime

99.67%

99.75%

99.98%

99.99%

Typical months to plan and construct

3

3-6

15-20

15-30

First deployed

1965

1970

1985

1995

 

 

 

Tier I

Tier II

Tier III

Tier IV

Active capacity components to support IT load

N

N+1

N+1

N after any failure

Distribution paths

1

1

1 active and 1 alternate

2 simultaneously active

Concurrently maintainable

No

No

Yes

Yes

Fault tolerance (single event)

No

No

No

Yes

Compartmentalization

No

No

No

Yes

Continuous cooling

load density dependent

load density dependent

load density dependent

Yes (Class A)

 

For the sake of completeness, please let me underline that, however, Uptime Institute Tier Classification is used to measure data center availability and operational sustainability by many auditors it is usually just a point of general reference. To formally conclude, whether given data center is Uptime Institute's Tier classified, its not enough to measure our site against the requirements on our own. We have to employ Uptime Institute Professional Services company, which is the only firm licensed to rate and certify designs, constructed facilities, and ongoing operations against the Uptime Institutes's Tier Classification System and Operational Sustainability criteria. Now, it's clear – however, we must agree that all the requirements presented in the above tables can be effectively used during data center design stage as a point of reference.

 


Well... This presentation on Uptime Institute's Tier Classification System is so different. It is published by user colocationamerica on Youtube


Moreover, it's good to know that Uptime Institute's Tier Classification System is not the only standard referring to data center availability and sustainability in the world. The other important one is defined by Telecommunications Industry Association, which is a trade association accredited by ANSI (American National Standards Institute).

In 2005 it published ANSI/TIA-942, Telecommunications Infrastructure Standard for Data Centers, which defined four levels (called tiers – see the similarity?) of data centers in a thorough, quantifiable manner. TIA-942 was amended in 2008 and again in 2010. TIA-942:Data Center Standards Overview (click for full description in PDF) describes the requirements for the data center infrastructure.

The simplest is a Tier 1 data center, which is basically a server room, following basic guidelines for the installation of computer systems. The most stringent level is a Tier 4 data center, which is designed to host mission critical computer systems, with fully redundant subsystems and compartmentalized security zones controlled by biometric access controls methods. Another consideration is placement of data center in a subterranean context, for data security as well as environmental considerations such as cooling requirements. According to ANSI/TIA-942 we can distinguish the following requirements for all four tiers:

 

  • Tier 1 – Basic: 99.671% Availability
    • Susceptible to disruptions from both planned and unplanned activity
    • Single path for power and cooling distribution, no redundant components (N)
    • May or may not have a raised floor, UPS, or generator
    • Takes 3 months to implement
    • Annual downtime of 28.8 hours
    • Must be shut down completely for perform preventive maintenance

 

  • Tier 2 – Redundant Components: 99.741% Availability
    • Less susceptible to disruption from both planned and unplanned activity
    • Single path for power and cooling direction, includes redundant components (N+1)
    • Includes raised floor, UPS, generator
    • Takes 3 to 6 months to implement
    • Annual downtime of 22.0 hours
    • Maintenance of power path and other parts of the infrastructure require a processing shutdown

 

  • Tier 3 – Concurrently Maintainable: 99.982% Availability
    • Enables planned activity without disrupting computer hardware operation, but unplanned events will still cause disruption
    • Multiple power and cooling distribution paths but with only one path active, includes redundant components (N+1)
    • Takes 15 to 20 months to implement
    • Annual downtime of 1.6 hours
    • Includes raised floor sufficient capacity and distribution to carry load on one path while performing maintenance on the other.

 

  • Tier 4 – Fault Tolerant: 99.995% Availability
    • Planned activity does not disrupt critical load and data center can sustain at least one worst-case unplanned event with no critical load impact
    • Multiple active power and cooling distribution paths, includes redundant components (2 (N+1), i.e. 2 UPS each with N+1 redundancy)
    • Takes 15 to 20 months to implement
    • Annual downtime of 0.4 hours

 

Finally, let's try to answer which classification is the one that suits your needs most? As always – find your own criteria and answer yourself. My recommendation – feel free to be inspired by both.

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