




a) Data center performance
b) Investment
c) ROI (return on investment)


  • Tier 2 = Tier 1 + Redundant capacity components.

Data Center Availability According To Tiers


  • Tier 1: Guaranteeing 99.671% availability.
  • Tier 2: Guaranteeing 99.741% availability.
  • Tier 3: Guaranteeing 99.982% availability.
  • Tier 4: Guaranteeing 99.995% availability.

Further recommended readings:

Posted by: Vivek Gite


98 comment

    1. If you still need to know anything about data centres email me your specific questions and I will reply

        1. Susan,
          There are 3 core standards in the industry. Uptime Institute Tier Standard:Topology, TIA-942 Telecommunications Infrastructure
          Standard for Data Centers, and BICSI 002-2011 Data Center Design and Implementation Best Practices.
          For BICSI and TIA, there is no “Certification”. Many companies will claim to provide “TIA” certification, but all they are really doing is an audit against the TIA “standards” criteria. I quote the word standard because the component that is deemed the TIA-942 DC Tiering is NOT part of the standard. It is an Annex (G) of TIA-942, and states clearly at the start of that section “This annex is informative only and is not part of this Standard.”
          Uptime Tier Standard:Topology is not backed by a standards body, but that doesn’t diminish it’s usefulness. However, only Uptime Institute Professional Services can officially certify a DC as Tier (anything). For more information on this, see my postings on http://www.tek-tips.com and Tier Standards 101.
          BICSI 002 have released a detailed standard document and as a “holistic” standards document is the only ranking that is party of an officially certified standards body. That said, they I have yet to see any data center actually use it as the basis for design or operational resiliency. Like TIA there is no “Certifying Body”, only group that says they have compared your site to their interpretation of the BICSI standard.
          Depending on your objective, I can certainly help you. Feel free to email me at spayton@gmail.com, and we can discuss further. As mentioned, for more information, see my moderated forum on Tek-Tips.
          Hope this helps.

      1. Hi Tony,
        Appreciate you can inform us if Tier 3 data centers require Access control and fire suppression as a must or not

      2. My company had asked me for a web search related to the specifications required for installation of data center in a hospital that had to connect 200 computers and 50 CCTV cameras. I have tried to search everything on net but cant find any thing relevant please do help me what is the accurate data that I have to search on the net

        1. Hi Ammar, are you looking for data centre specification or the IT infrastructure for the hospital? i guess the specification will vary and you will not find a straightforward suggestion. my suggestion for you is to sit with a IT service provider and discuss. if the hospital is big, you will need to design a reliable network since the interconnection distance is far.

      3. Dear Tony,
        How can I communicate with you. Could you please place your email ðŸ“§ id.

      4. I am going to setup a tier3 datacenter. But i dont have any information regarding tire3 DC. Can anyone please help me by providing TIA 945 TIRE3 DC documentation? Please send the documents on below ID.

        1. Juyal,
          The TIA-942 (current version 2014) is not a free document. You have to buy a copy, which is available online or as a hard copy. For non-TIA members, it’s $450.
          If you don’t have experience with the standard, you should consider taking one of the DC certification courses, as it will get you up to speed fastest. While there are several courses available, EPI have course for DC engineering, leading up to TIA-942 design certification. If you just buy and read the document, it’s probably not going to be a great help to you. The devil is in the details.

          You can also visit my running discussion and blog where TIA and other standards are discussed at:


          It will get you started. If the link doesn’t work, go to tek-tips and search for “Data Center Discussion” forum.
          Best regards,

      5. I’m applying for a TL role in a data centre
        Would like to know hardware side of setting up servers and AD administration in data centres.
        Can you point me in the right direction where I can gain a general idea and ideal setup process in data centres as to get general idea and keep up spilling..
        I do have some knowledge about servers but reading and having book knowledge is going to help me.
        You help will be greatly appreciated

        1. Sreekanth,
          For deployment, you will want to look more at things like configuration and release management, in the ITIL or ISO 20000 disciplines. This is more a IT Service delivery function than would be a “Data Center” function. The implication of deployment in a DC can be a little more specific. The key things to consider beyond the typical “IT” server deployments are:

          Does the cabinet have enough space to put the server in?
          Does the target cabinet for server installation have the right source of power (i.e. ~100v, ~200v)
          Does the target cabinet have enough power capacity? (i.e. how many amps will this server draw, vs. the breaker it is attached to?)
          What is the resiliency of power required? (Is the server equipped with dual power source? Are there 2 power strips that it can be connected to in the rack?)
          What is the total weight of the rack and it’s contents? (Can the floor support more weight added to the cabinet, or is it already at maximum?)
          Is there enough cooling capacity in the rack to accommodate the heat load that will be increased by addition of this server?

          These are the critical infrastructure considerations, but if you want more around server deployment and service delivery, see ITIL ISO.
          Hope that helps,

      6. Can you email me the type of security center Ashley Madison had for its data?
        Im curious, as a company in my vertical is often boasting that they are a Tier 4 security center. I think it’s just sales buzz, but I want to have a retort, should it be thrown into my face.

      7. Hi Tony Graddon,
        I am glad to see about your reply that to need any info about Data centers.
        Am working as Network Engineer in Data Center, am looking all the infrastructure maintenance requirements.
        So, i want to learn more about Data center Infrastructure management.
        Could you please…

    2. hi sudish,

      put your queries to this email id for solutions and stuff u need anything related to DATA CENTER. I am Infrastructure Solution Architect working for MNC since 9 yrs in Data Centers. thnx. Teja

      1. Hi Teja,
        Could you please…

    3. Hi ,

      Good day !

      I would like to know if i am going to deploy oracle and i am having already one rate with 3 servers on windows and now we going to deploy new machines and with more reply ability so please guide me what should i do because existing one is not big designed data center its just like a partition room where i have installed 5u rack and installed the system but int his room some time AC goes slow automatic than we need to complain vendor to fix so thts kind of issues i want to avoid and make simple and secure data center .


    4. Hi,

      Can you send me a link on Data Center for dummies. I basically need to study how data center works, what are the components and its functions.

      Also, if you could provide a diagram or a drawing maybe for me to picture out how it is structured. Appreciate your help.


  1. hi… ambrose here,

    Very soon im going to sit for CDCP exam;
    anyone give me some tips.?
    how should i prepare for the exam?

    1. Hi Ambrose.

      I am in to Racks IT solutions , And also promoting inrow and licquid colling solution.

      Can u please suggest me what are the level to get certified data centre associates.

      Like APC offering DU0-001 which is best

    I want to learn about data center. So please give me easy understand hint about data centre.

  3. Hi There,



    1. For God’s sake! You are going to setup and tier3 datacenter and you have no incofmation about it?……

  4. Hi,

    I want to know the lumen/ft2 of a data center and also what tier is all about.



  5. Hi,

    I want to know the lumen/meter square of a data center and also what tier is all about.


  6. We want to know what is the minimum UPS battery backup time recommended for lebel 3 Data Centre in India? Where can we get documentary evidence in support of that?


  7. Hi Everyone,

    Has anyone ever produced a report on data centre environment usage, that is calculating the usage of cooling systems, Power and etc. Please if you have, I would like to produce something like that. Help. It is like a data centre capacity plan.


  8. I want to be a data center facility manager. Kindly give a directory to an online viable institution that can enable this.

    Many thanks,


  9. I’m looking for the same type of information that Collin Nakedi requested. We’re gearing up to build a new “green” data center and i’d like to get ahead of the power requirements so they are included early in the design considerations.

  10. Can a datacenter remove redundant data or should we keep it? I have a datacenter m&o job interview and need to know as fast as the reply comes.

  11. i am a data center specialist i installed so many system i need the knowledge of tier 4 cdcd, cdcdp,BICSI,RCDD,ATD

    1. Actually, this article is very misleading, and fraught with mistakes and inaccuracies (at best).

      Tier , to answer Pascal’s question, refers to the gap between level of capability between each of the DC benchmarks. It’s not a “magic” term. (You could say, Tier, Level, Category, Rank… they all mean the same thing, but the industry has adopted “Tier” as the terminology to use for DC capability).

      None of the Tier ranking systems (Uptime, BICSI, TIA) “guarantee” any % of uptime. They are an indicator of how likely your uptime will be, and how one should benchmark against it. Where this all goes horribly wrong, is the Tier rating for all these systems takes into account only the “Built” specification. None of them consider (at Tier rating) how a site is maintained. (Uptime now address this with Tier Standard: Operational Sustainability). So no Design or Redundancy can guarantee a % of availability.

      Regarding Uptime’s Tier, this really is focused on: “Power in, Heat out”. These references to redundant storage, servers and coms is not part of the Tier classification, beyond the need for dual-corded systems in Tier III and Tier IV. (Note also Uptime use Roman Numeral, not Arabic for classification. This is because there is no “Tier III.6” or “Tier II.v”)

      For Tier III and IV, it is also necessary to have redundant generators that are Continuous Rated (as opposed to Prime or Standby rated). And Tier IV requires compartmentalization of capacity systems to no more than R (redundant) per space (2 hour fire-rated rooms).

      BICSI 002-2010 was just released last year. I’m in the midst of reading it, but I’m disappointed that it has a heavy leaning to US implementations. I’m not calling it “US centric”, but there cases or references (such as site selection) have all US maps and site data on them.

      TIA-942 addresses data cabling in data centers. There is no certification of a site to “TIA”, where there is a certification to “Tier Rating” with Uptime. TIA-942 has a number of “Tier” data in its appendices, but this isn’t really a rating/ranking system that has a measurable certification, more like ITIL, where you can be “ITIL compliant” but there is not “ITIL certified”. It is the same for TIA.

      1. Regarding your comment “Uptime use Roman Numeral, not Arabic for classification”, I just wanted to tell you that the numbers 1,2,3 etc are Indian and not Arabic. Infact Arabic knew nothing about education and learning, and hence they could have invented nothing.

        1. Vijay , Arabs have invented a special number which is 0 . it still can be assigned to the knowledge o internet trolls. At least do yourself a favor and read Wikipedia to get your facts right .. Arabic numerals are the numbers the West is using now. Arabs have always been in a cultural exchange with west and east…something for you to learn

  12. Hai friends i am going to learn CDCP COURSE .can anyone help me for sample question and documentation.If any site available.pls let me know.

  13. Hai,
    Those who are brilliant in datacentre technology share your briliance for the foll.

    1.Rack allocation for server,router,switch,kvm and future expansion how?
    2.How the building space chosen?
    3.How the cooling chosen ? i.e ( centralised or packaged unit etc..)
    4.Any std to be for maintain for data cable laying,Termination of I/o,testing etc.?
    5.How electrical power is calculated for rack,Ac,lights,ups,gensets any specific rules or calculation for those items.?
    6.raised wooden flooring specification and std.?
    7.security system for camera , fire alarm,access control type etc to be explain.if any std pls explain.?
    8.false flooring type and specification for the same.?
    9.Lighting type,PDB,LDB,MDB etc to explain?

    pls share your brilliance,

    Thanks with regards,


    1. Mohan,
      The questions you ask are too extensive without understanding the business objectives. Plus, this kind of thing is what consultants get paid to do… it’s unlikely you will get a “full reply” about all the items you mention. The level of effort to respond in a meaningful way to all of this would take weeks to explain.
      If you have some questions, you can email me directly at spayton at gmail.com I will give you guidance, but without understanding what you’re trying to achieve, this is like asking someone to explain, in full detail, how to construct a 140 story skyscraper, with no more detail then that.

  14. Please can anyone clarify this? Do you have to have a dual power supply into the site to be Tier III compliant or can you be Tier 3 if you have redundancy inside the building?

    1. Hi Janice,

      According to my knowledge. You need to have Dual Power Source for TIII rating DC.

      Vinay Kumra

      1. Vinay,
        Please read my full post. If we are discussing Uptime Institute Tier Standard: Topology, from the 2010 revision, “Dual Power Source”, if we are referring to utility power source, is not required. In fact, for any Tier I – Tier IV, NO utility power sources are required, though they are frequently utilized as a low-cost alternative to commercial power.
        If you are comparing to Appendix G of TIA-942, in their suggested “check list”, of DC items, Tier 3 and Tier 4 of the 2010 list do require utility power source redundancy (be definition they define Tier 3 as N+1 Utility feed, which means minimum 2, but could require more, and Tier 4 needing 2N power feeds from separate utility substations (meaning, 4 feeds!) which in my view has no value, as power grids will fail, and regardless of the number of stations providing their power, the grid can still fail. This results in millions of dollars in investment, and yields no value when the power goes out.

  15. Janice,
    There are a few parts to this.
    First, let’s identify the standard. You mention both Tier III and Tier 3. First is designation for Tier under Uptime Institute. The second one (with Arabic number) is TIA-942 designation.
    I’m going to assume in this case, we are talking about Uptime Institute. Under Uptime Institute, you are asking “Dual Power Supply” inside or outside. The answer here, is both from a certain point, and probably more than just what your question is asking.
    Let me try to clarify.
    Tier III (or 3) in both cases is defined as “Concurrently Maintainable”. What that means in this case is, for your power system you must have the ability to remain under critical load (N) while performing maintenance (on your power or cooling systems). For power, that will mean you will likely have A and B power feed, which may or may not both be active at the same time. This will mean you will have at least N+1 UPS (usually on each feed, but there are other options, I’m just using this as an example) which would give your UPS (2)N+1 meaning you have N+1 on A and N+1 on B power feeds. Going back to the source however, this can be a little un-obvious. The reason being is for Tier III and IV sites, the generator set is considered the primary power plant. It is not necessary to have 2 (or even 1) utility power feed to meet the Tier objective, so long as the generator plant is properly setup and configured. I’ll skip that detail for now, as it’s going in the different direction to your question.
    So, from power source (Gen or Utility) you need redundant components (Switches, UPS, Batteries) and redundant pathways for power (At least one active, the other passive, though both active is also allowed), leading to your critical IT load, as well as to your Mechanical Load (though Mechanical Load does not have to be on the UPS for Tier III). The last “gotcha” in the Tier III power issue is dual corded IT equipment. The IT gear itself (Server, Switch, SAN, data circuit) must be dual corded, with one plugged to A feed and one to B feed. If only single cord (as some data circuit gear), then it has to be plugged to an ATS or STS in-rack that then has dual feed cord connection to A and B power feeds.
    TIA is not terribly different, as for the largest part they have borrowed an older Uptime Standard for Tier system which follows about 90% of the Uptime standard. Dual corded in TIA is also required. However, under the new TIA-942-2 standard, Utility Power Feeds for Tier III are designated as N+1 (Which would mean, you would need at least 2 in most cases, or more if any 1 utility feed was not enough power to carry the DC load). The rest of the power issues going forward from that point are the same as Uptime Institute.

    If you need more clarity around the engine generator plant let me know but that didn’t seem to be your question, and there are significant gaps in this space between the two standards.

    I know it’s a little convoluted, and I hope this helps.
    Best regards,
    Scott Payton ATS, CDCS

    1. Dear Scott ,
      would you please provide more clarity around the engine generator plant and whether to use single ATS for the load inside the Data Center (UPS+Cooling system , etc..) or its better to segregate the load e.g one ATS for UPS , another one for Cooling system>



    2. Scott,
      Your comment,
      “though Mechanical Load does not have to be on the UPS for Tier III”
      was the only portion of your response to Janice that left me confused about your understanding of mechanical loads (induced current) incorporated into a UPS design. Standard industry practice does not place mechanical loads on a UPS source. Maybe you meant to say that mechanical loads within Tier II and Tier III systems incorporate reduntant power supply as well. Static transfer switches can be utilized for this application or a more realistic and cost effective application is a manual transfer switch utilizing a kirk key configuration for safety.
      Further, single corded IT equipment normally does not get “pluged into” STS (static transfer switches) or ATS (automatic transfer switches) single cord components are normally plugged into power power strips that are typcially fed from mutiple power sources such as distribution units (PDU’s) or in some cases the STS is of small size and compatibility that it is located close enough to the load as possible providing power receptacles for small loads such as pc’s.
      Looking forward to your comments on switchgear, tie breaker configuration, control logic and sequencing and generator configuration.

  16. who will be the certification body for Tier III & Tier IV , Any consultant / Expert can issue the certificate of Tier III & Tier IV
    what are the standards to follow for Tier III & Tier IV certification for data centre
    do you hv any checklist for that

    1. Nanda,
      Two issues here… There are two “standards” that utilize the term “Tier” as their rating system. Uptime Institute use Tier I – Tier IV (roman numeral) while TIA-942 utilizes Tier 1 – Tier 4 (Arabic numbers).
      There are no certifying bodies for TIA-942. Several companies may claim to do “TIA-942 certification” but this is meaningless. At best they can compare as-built to TIA criteria, and assess that it meets or does not meet in their opinion.
      For Uptime Institute, only Uptime Institute Professional Services can provide an official Certification. This is regardless of the Tier level, so they are the same body to certify a DC as Tier I as Tier III (or any other Tier level).
      Hope that helps.

      1. Can any one help me ,how to contact with uptime for my Tier-III Data Center Certification

  17. Sun,
    Tier III (or Tier 3) does not specify the type of fiber termination. It’s not part of the Tier standard. There are likely opinions on “best practice” for fiber termination in Tier standards.

    This whole thread seems to be way off topic of UNIX world… I would suggest visiting Tek-Tips (www.tek-tips.com) and join my moderated DC forum there (Data Center Discussion).
    Best regards,

  18. Hi Scott,

    We are in the process of setting up a data centre in Africa. We are hoping to achieve a Tier III status on this data centre as we will have redudant power supply (Power from the Electricity company Sub Station + 2 x Standby Generators + UPS’s to protect the racks and equipment hosted in the racks), Redundant Data Connectivity (Fibre connectivity + Satelllite for Failover) and Redundant Cooling within the data centre (two cooling units in case of failure). Now iv been reading so many articles online and has proven almost impossible to understand if this actually does meet the Tier III Standard or it will only meet a Tier II.

    I would also like to know how you actually get the certification done once your data centre is built? Is there a specific organisation that you need to contact and they do the assessment and certify accordingly?

    Lastly, regarding the cooling within the data centre. Many have indicated that water based chiller systems are more appropriate but others are dead against water based systems and suggest Gas based systems due to power efficiency especially in countries where the Lime content is high in the water.

    Would be great to get your feedback.



  19. BejoyN,
    Since this thread about DC has gotten “out of hand” on a Unix site, can you please come to Tek-Tips (www.tek-tips.com) and ask these questions in the Data Center Discussion forum? I’m trying to corral all the information into one site, where others can benefit from it.
    Repost there, and I’ll answer all your questions.

  20. Ksomer,
    Please direct all DC questions to the “Data Center Discussion” forum on the site http://www.tek-tips.com I’m no longer following this thread here. You can post anonymous on Tek-Tips, or create a login, please.

  21. Working on a RFP that requests data centers to be as per the Lanyon standard, can anyone advise where I could find more info or what this standard is?

  22. Tom,
    The comment about mechanical loads on a UPS is specifically in reference to CRAC units connected to UPS to achieve Tier IV requirement for Continuous Cooling under TS:T. It is HIGHLY advised to provide mechanical load of this type with its own UPS, and not use the same UPS source as the IT gear.
    Regarding single corded equipment, if the rack is fed by multiple PDU which have STS at their sources (PDU also fed by two sources) then in-rack PTS (Point-of-Use Transfer Switch, which can be either STS or ATS) is not necessary. Otherwise, for Tier III and Tier IV under Uptime Institute standard, a localized (in-rack) PTS will suffice. It obviously can’t account for PSU failure in a single device, but at least provides power in the event of loss of a feed (A or B) source.
    Does that clarify?

  23. Hi there, Can someone elaborate for me on what is meant by a “single uplink” (as given as part of the definition of a tier 1 data centre installation)? That would be much appreciated, cheers, M.A.

  24. I just want to knw about tier 1 and is it belon to Server support and wht is basically the work in server support ? and is there chance of growing urself and how lon u grow in ur career ?

    1. Abhijeet,
      You should download the Tier Standard: Topology and Tier Standard: Operational Sustainability from the Uptime Institute web site. It will help you understand what is and is not contained in the Tier rating. Server support has 0 to do with Tier rating. There are many training programs you can enter to improve your DC design and practice capability. DCD, EPI, Uptime Institute, CNet all offer DC programs. Some of them are progressive, others expect you have a certain level of capability and background first.
      Best wishes,

  25. Does anyone know a company that can use a project manager with five years of managing data center infrastructure? My experiences are in Tier 4 data centers from fiber optics connectivity to San & storage work. I am located in Atlanta GA.; however, I am open to travel.

    1. Hi Vipul,

      here is the simple calculation for Data Center Cooling provisioning.

      1 KW = 3412 BTU (British Thermal Unit)
      for example: u have below racks in ur DC say,
      23 racks of 3 KW
      10 racks of 5 KW

      So total KW is how much, let us calculate here:
      23×3 = 69 KW
      10×5 = 50 KW
      Total is 119 KW.

      119kw x 3412 = 406028

      Now, required Tier will be 406028 / 12000 = 33.83 Ton

      Note: 1Ton = 12000 BTU

      Summary: U need 33.83 Ton of AC requirement for your Data Center.

      You can go for 17Ton x 3 No. (precision AC) here N+1 methodology you can opt.

      17 ton x 2 will be Live / production
      17 ton x 1 will be Redundant (Standby)


      1. Millica,
        Compared to what? This has to be put into business context. Return on investment and added complexity of Tier IV often put them at risk of either a) over capitalizing your DC, or b) resulting in MORE down time because complex systems are not thoroughly thought out and tested.

  26. I am Networking guy, I want to know what type of devices has been used in google data center, those are cisco gear or juniper gear or what – (in Networking and security field).
    if someone can provide that info. – that would be greatly appreciated.
    Thanks in advance

  27. Ø³Ø±ÙˆÛŒØ³ Ù‡Ø§ÛŒ Ù…Ø±Ø§Ú©Ø² Ø¯Ø§Ø¯Ù‡ Ø¨Ø± Ø­Ø³Ø¨ Tier Ú†Ù‡ Ù‡Ø³ØªÙ†Ø¯ØŸ

  28. Hi

    if any one wants to know about DATA CENTER knowledge, TIER standards, any queries, understanding on starting up Data Center. What Infrastructure to be used, Monitoring, Certifications, kindly contact me. thnx. Teja

    email: career14cni@outlook.com

  29. please send the solution for â€¢ Tier 1,Tier 2,Tier 3 , Tier 4

    what are requirement and best practice to be used

    1. Shareef,
      Your question is too vague and there are multiple standards, and “Tier” doesn’t mean the same across all of them. For a starting point, please see my discussion form “Data Center Discussion” on tek-tips, where you can find information, and post follow-up discussions (http://www.tek-tips.com/threadminder.cfm?pid=1786). I no longer make technical replies in this thread.
      Best regards,

  30. Hi!
    I have to work on an assignment.
    I am asked “what are different tiers of data centers? Explain in detail.
    Also design a tier1 data center for a nationwide cellular company then gradually upgrade to tier2, tier3 and finally tier4, sharing the upgradation steps.’
    Can I get some help in the matter?
    Mudessar Rahim

  31. Hello,
    I’m preparing a business proposal to a telecommunication company who wants to open a subsidiary in Africa. So, I was requiring your expertise and knowledge as a guide in setting up of a Tier 4 Data centre. What are requirements and costs involved? And how could we assess the risks?

  32. I am going to do the electrical design for TIER 4 data center. Can anyone please send me the electrical single line diagram so i can have an idea about TIER 4 redundancy requirements.

  33. I am going to do the electrical design for TIER 4 data center. Can anyone please send me the electrical single line diagram so i can have an idea about TIER 4 redundancy requirements. You can send me the files on the below id.


  34. Hey could you help me with the information regarding the pricing of one data center in relation to space as well as cost.

  35. Thank you all for such helpful information.

    I am Data Centre engineer since last 2 year.I want to make carrier as Data centre consultant, can any one guide me which organisation offers certification of consultant ?
    Is CDCP course is reuire for become consultant ?

    Kindly update me for this.

  36. What is your opinion on having the critical areas of data centers professionally cleaned? Example is having the raised floor cleaned and vacuumed with high filtration environmental vacuums and lint free wipes . Cleaning under the floor space and wiping down the equipment cabinets not touching the critical components to remove particulate contamination in the data center. Do you think this is a necessary process to maintain a data center. Or I guess I should ask do you do this or recommend this for data centers?

    Thanks for your time and input.

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