In the end, 'cloud' is pretty amorphous.  In general, it refers to one of the three types of service: Software as a Service, Platform as a Service, and Infrastructure as a Service.

Service means:

1. User can sign up by his or her self without 'talking' to anybody.  This includes payment if necessary.
2. Broad availability (either within an intranet or on the Internet at large).
3. Multiple tenants participate.  These may be different groups within an organization or different entities outside any one organization.
4. Scale 'infinitely' as far as the end-user is concerned.  This obviously isn't true infinity - it just means that the user isn't worried about the underlying ability to scale.
5. Measurement - can the end user see whether limits are about to be hit.

Public vs. private is mostly around #2 and #3.  If the 'service' is accessible on the Internet, it's public.  If it's not, then it's private.

Infrastructure = compute and raw storage
Platform = programmed resources that you hit with an API (i.e. a database as a service platform)
Software = End user applications - Gmail would count here since it offers email client software.

A cloud includes any of these services.  If somebody sets up a few machines in their office, it's not a cloud unless other groups in the organization can use those machines without talking to the person who set them up.  All 5 items above should be met in order to refer to it as a 'cloud'.

-Adam

--
Kili - Cloud for Africa: kili.io
Musings: twitter.com/varud
More Musings: varud.com
About Adam: www.linkedin.com/in/adamcnelson


On Tue, Apr 15, 2014 at 9:29 AM, Mwendwa Kivuva <Kivuva@transworldafrica.com> wrote:
On 15/04/2014, Tech List Kenya <techlistkenya@gmail.com> wrote:
> So basically, if I buy 1 powerful server, install ESX and then on top
> of that install 2 OS - win server for Exchange, Linux server for an
> Erp, can I say I have setup a private cloud?
>
> What if I install Win server first instead of esx and then as guests,
> install another win server and a linux server, ref above. Does that
> still qualify as private cloud?
>
> If I buy IaaS from kili.io or angani.co or Amazon, is that still private
> cloud?
>
>
> On 4/15/14, Tony Olendo <tony.olendo@lrcafrica.org> wrote:
>> :)
>>
>>
>> Sent from Samsung MobileMutinda Kitana <geniusphere@gmail.com>
>> wrote:Techlistkenya,
>>
>> It's interesting you should mention clouds now, I had the very same
>> question
>> last week. From what I've learned, cloud is different in that it works
>> like
>> a raid array. A cloud OS is installed across several servers (one being
>> the
>> controller) and then a hypervisor (Vmware or Xen) is installed on top of
>> that and finally operating systems are installed inside that. The cloud OS
>> treats the servers (hardware) like they are one big server, just like a
>> raid
>> controller treats several disks as one.
>>
>> So, in case one of the servers goes down then services are still
>> available.
>> Also 'clouding' helps with load balancing. Resources like storage space
>> and
>> processing power are divided across all hardware and any that isn't needed
>> can even be turned off.
>>
>> Regards,
>>
>> --
>> Mutinda Kitana
>> Project Manager
>> GENIUSPHERE
>> Cell: 0722-944455
>> --
>>
>> Don't worry about getting motivated.
>> Just get going.
>>
>> ~ Borrowed
>>
>> On Mon, Apr 14, 2014 at 4:29 PM, Tech List Kenya <techlistkenya@gmail.com>
>> wrote:
>> Guys,
>>
>> I think am getting confused by the cloud jargons. What exactly is the
>> difference between private cloud and datacenter?
>>
>> I am using the term data centre very loosely here to mean the corporate
>> internal IT infrastructure
>>
>> There is a lot of talk about setting up private clouds yet in my opinion
>> this has been there for ages. Doesn't corporate file server, exchange
>> server, etc constitute a private cloud?
>>
>>
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twitter.com/lordmwesh
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