Public vs Private Cloud – which is better

17 Dec

Cloud Image Success and FailureCloud Adoption Trends – Is Private Right?

There’s an amazing amount of teeth gnashing around private vs. public cloud these days, much like in previous days. In this case though I’m not going to even entertain the discussion on whether private cloud is real, rather I’m going to talk about how different IT organizations might approach a cloud decision considering their own unique variables.

There isn’t a one size fits all answer

Nope, cost isn’t the answer, technology architecture isn’t the answer, and security isn’t the answer either. In fact, no one answer is correct, but in some cases all of them are. The first priority for the business is running a successful enterprise. The first priority for IT is to provide solutions that help the enterprise achieve that success however the business chooses to measure it. In other words, the right answer is the one that best enables the success of business objectives. The right answer could be private, public, mainframe or all of the above, and that answer will be dynamic, just as modern business is.

Common Private vs. Public Cloud Decision Themes

There are a wide range of requirements that the industry and those of us who write about cloud have used to try and convince you are always best. I’m here to say that there is no “always” when it comes to picking IT solutions and cloud is no exception.

Public Cloud Themes

Private Cloud Themes

Massive scale requirements Control
Cost Security
Staffing Cost
Geo-Distribution requirements Support structure
Speed of access & delivery Compliance
Options Steady consistent business growth
Ecosystem of partners Agility
Support structure Well understood usage
Agility Ecosystem of partners
Elasticity at scale Speed of access & delivery
Compliance requirements Compliance requirements
Rapid Business Growth Legacy Applications & Infrastructure


Weird huh

No, your eyes aren’t deceiving you what you’re seeing in the above table is in fact true, many of the supposed “drivers” for selecting public vs. private (in the right circumstances) apply to both options. The magic is in where and how each of the above variables applies and what importance they should be given.

Each company must make its own value judgments

Cost is still often identified as a key benefit of cloud adoption, as is massive scale, geo-diversity, and elasticity at scale. The issue with any or all of the aforementioned cloud “qualities” is that they only matter under the right set of circumstances. There is incredible complexity associated with defining the best option for each company at the time they’re making the choice, and as such, the following three scenarios have been simplified. I’m sure that if I attempted to cover every scenario I would need at least 100 different models.

Scenario 1: 20 plus year old mid-size enterprise (Not internet driven) 

Legacy 1000 plus legacy applications Many won’t be moved to cloud (any cloud) for 5 years or more
Staffing Small IT team with limited developer skills Likely to want packaged solutions that allow them to gain rapid benefit, even with a cost premium
Well Understood Usage Applications are well understood in the usage characteristics (limited short term scale needs) Having limited elasticity requirements means the “massive” scale of public cloud doesn’t provide additional value
Agility in moderation Agility is desired for competitive advantage Rapid delivery is important but not measured the same way as an internet driven business (Days vs. months is OK).
Steady moderate growth Business growth of 7% or less CAGR Growth implies fewer surprises for IT requirements at scale
No real geo distribution needs Limited geographic diversity requirements of apps Have a few locations but primary app usage is at HQ


The likely answer for Scenario 1 is private cloud, with public cloud used for a few applications and some development. The fact that the majority of workloads are well understood and don’t experience significant usage spikes means that a slightly over provisioned private cloud environment is likely more cost effective in the long run. The limited size and experience of the team also means they would most likely benefit from a packaged cloud solution (converged infra with a CMP). As speed isn’t the primary requirement and there are only a few key office locations the need for a widely distributed public cloud based application set is diminished as well. The focus for new applications should be on SaaS wherever possible.

Scenario 2: 7 year old internet facing business

Legacy Apps Limited set of legacy applications Active projects underway to retire all of them as opportunity provides
Staffing Good sized IT team focused on enabling an internet driven business model Focused on solutions that can scale and scale at a manageable cost.
Elasticity, Geo-Diversity, Support structure Primary applications are internet facing and each of them can vary wildly in use depending on product launches and seasonal buying patterns Elasticity at scale is critical, along with an ability to rapidly deliver updates.
Agility Agility is desired for competitive advantage Agility is measured in hours vs. days and applies to the entire company
Rapid growth, geo-distributed, Internet oriented Business growth of 15% or more CAGR Growth can be volatile and difficult to plan for
Geo-distribution Widely distributed work force with developers and contributors in offices all over the world. Also, a customer base that is globally distributed and dynamic. Geo-Diversity is critical for application, performance and fault tolerance


In scenario 2 the primary usage characteristics for the company (global distribution, speed to market, many locations for customers and staff/engineering) suggests that the focus should be put on utilizing public cloud for most solutions. If there are internal focused applications that are fairly steady in their use, then the addition of hybrid and or private cloud could make sense.

Scenario 3: 20 plus year old large financial Institution

Legacy Applications 1000s of custom built applications, some delivering millions in revenue Some projects to retire or move applications to stateless environments. Heavy focus on building new apps for cloud. Many existing apps impossible to move to public cloud
Staffing Large IT team focused on enabling large scale cost effective performance oriented infrastructure Solutions that scale, potentially involve staff investment in open source (I.e., OpenStack/CloudStack/RedHat/Automation, etc)
Elasticity, Geo-Diversity, Support structure Extreme elasticity applies to a few key apps for trading, Monte Carlo, big data analytics etc. In some cases this could be handled by public cloud/grid infrastructure. Some applications will be better suited in hybrid/private cloud
Agility Agility is a driver like most businesses, but is not the sole reason for cloud operations. Agility is measured in days vs. months
Steady growth, geo-distributed, heavy IT investment Business growth of approximately 12% CAGR Growth is fairly well understood
Geo-distribution Widely distributed work force with developers and contributors in offices all over the world. Also, a customer base that is globally distributed and dynamic. Geo-Diversity is critical for application, performance and fault tolerance
Compliance Heavy regulatory and compliance based risks Require contractual guarantee with providers or internal solutions


With scenario 3 the environment is fairly complex and doesn’t fit into a single solution. The fact that they have a strong IT team and fairly large internal set of applications means private cloud is a real option for them. They are also likely in a position to be able to develop unique private cloud environments instead of focusing on pre-packaged converged infrastructure. However, public cloud is potentially an ideal solution for some of the customer focused applications and or applications requiring elasticity at scale. An open item is compliance; using public cloud would depend on the provider’s credentials along with usage trends for any given application.

It Depends

As you can see from the definitions of each company’s unique environment and how those unique needs help define the priorities and strategy for technology adoption, there isn’t a one size fits all option for cloud. My belief is that for the next 5-10 years we’re likely to see the majority of companies with over 200 employees using a hybrid set of cloud based solutions, which include private, public, hybrid and SaaS. Farther down the road, who knows, maybe we’ll get to the magical low cost commodity cloud that will suit all.

Use the scenarios

Using the scenarios provided as a model, you should be able to ascertain some of the critical decision factors in making a cloud choice for your organization. Having a firm grip on what your teams are capable of, in combination with what a specific solution requires will help you to better position IT as a partner instead of a roadblock.

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  1. Ben Ferri

    December 17, 2013 at 3:50 pm

    Public Cloud vs Private Cloud: Which is better? = Both!

    Nice article, this is spot on. It really depends on the organization’s needs. For some organizations, a mix of private and public is the best fit.

  2. Rajesh

    December 18, 2013 at 6:48 pm

    Well done. Brief, but, comprehensive and informative. Have a wonderful Christmas. Rajesh

    • Mark Thiele

      December 19, 2013 at 4:43 pm

      Hi Rajesh,

      Thanks for the comment. It’s always great to hear from you.


  3. Ranga

    December 19, 2013 at 3:53 am

    In the first use case if they don’t have any self service, charge back & usage collection requirements won’t plain old virtualization be sufficient?
    I think first the culture and mind set to adopt cloud and give self service power to developers is a prerequisite before starting to look and which option best suits their needs.
    Great article though.


    • Mark Thiele

      December 19, 2013 at 4:43 pm

      Hello Ranga,

      Thanks for the comment. I can see your point and would agree that in some cases simple virtualization will suffice in place of a more complex cloud solution. However, its also true that many smaller orgs just don’t have the type of “developer” community that would drive the value of more complete self service offerings. But there are still considerable benefits to be had from a “cloudish” infrastructure that doesn’t have all the typical must haves that a larger more complex org would demand.

  4. Valdymo

    January 6, 2014 at 8:56 am

    Very interesting view of cloud types, it probably depends of business type, which is the best to choose. On the other hand why not to try to find hybrid and in the same way unique solution.

  5. Swarna

    April 14, 2014 at 6:03 pm

    You have made it so easy and simple that even folks like me can understand it so clearly. Very informational, educational and insightful post, Mark. Thanks for sharing.

    • Mark Thiele

      April 14, 2014 at 6:11 pm

      Thank you Swarna. I appreciate the comment.

  6. Col S Parthasarathy (retd)

    April 9, 2015 at 11:21 am

    Nice article. Very lucid and insightful presentation. Interesting comparisons and scenarios. Preferred option should enable gainful exploitation to further business objectives.

    Col Partha