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I read through a few discussions in SE about Cloud Computing . From them, I understand cloud as "computing / data-storage facility that is owned by a different entity; using hardware & software architecture that make it easily scalable on-demand, therefore support rentable-scalability models."

Also, "the owning entity has a big-size data center, where virtualisation concepts are put to use to cater to multiple different customers from same hardware". Plus "redundancy, security etc are assumed to be taken care by the provider. "

I read a discussion in SE about explaining Cloud Computing to grandmother. The 'garden vs supermarket', 'own-house vs hotel' examples suit perfectly.

With this understanding, I am unable to visualise 'private cloud'. Frankly, 'private cloud' sounds like an oxymoron to me. (relate with 'private supermarket' , 'owned hotel' etc). Pardon my ignorance.

So, what is 'private cloud' ?

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Think of it as a supermarket that's only accessible by certain people (i.e. only available for employees at xyz). –  Rob Jul 17 '11 at 23:46
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Proper analogy would be: "private cloud" - "private restaurant", "virtual private cloud" - "restaurant reserved and closed down for a private event". OTOH, "own-house vs hotel" is more like "dedicated server" vs "cloud" –  vartec Apr 22 '13 at 15:01

7 Answers 7

A private cloud is when a (usually large) organization creates a cloud computing infrastructure for internal use by its various departments, thus avoiding the security and "our core business depends on someone else's hardware" concerns.

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In other words, its just like an intranet. Internal services offered by central machines somewhere. (The wheel of the central computer department -> decentralizing -> centralizing just goes around and around, with spinmeisters to sell an old idea as a new one). –  quickly_now Jul 16 '11 at 8:03
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@quickly_now - A private cloud is completely different from an intranet. You can run a basic intranet from a PC under someone's desk. A private cloud implies a range of advanced capabilities (e.g. full stack virtualisation, automated provisioning of servers, redundant failover sites etc.). Yes it is all server infrastructure at one level, but it's like comparing a Cessna 172 to an A380.... you can't seriously suggest they are "just like" each other –  mikera Jul 16 '11 at 12:22
    
' A private cloud implies a range of advanced capabilities (e.g. full stack virtualisation, automated provisioning of servers, redundant failover sites etc.).' <---- and an API sitting in front of all of that for programmatic access to the infrastructure to control resources. –  whaley Jul 16 '11 at 17:59
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Yeah right. And I'm a cynic - it's all just the same old same old dressed up differently. –  quickly_now Jul 17 '11 at 2:52
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@quickly_now so by extension a non private cloud is just an intranet hosted by a third party.....aka internet? –  Pieter B Apr 22 '13 at 13:21

It doesn't really mean anything. Based on who is doing the talking it could mean:

  • your company's implementation of a cloud infrastructure (this is what happened at my previous company).

  • segments of a cloud infrastructure where your programs have much higher priorities than other (paying or not) customers.

  • nothing at all - the sales rep makes a claim that you cannot prove one way or the other, but charges you more for the "product".

When someone is trying to sell you on "private cloud" ask them what it means. If they can't explain it, or try handwaving/waffling with 'you know' (or something similar), then they are trying to con you.

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Yet another definition - we host our ASP solution in a private cloud based on VMWare. We have a resource pool (CPUs, memory, disk space) and several VMs. The hosting company can move our private cloud around if/when hardware fails or we can easily buy more memory/CPU/VMs when want without worrying about physical server capacity or downtime.

We will never go back to hosting on dedicated bare-metal servers. You can manage disks with RAID 5 and have dual power supplies or NICS but mainboard, memory chips etc give you a single point of failure.

A private cloud means we are not dependent on actual physical hardware, and we can quickly add another CPU without interrupting processing.

Our private cloud also comes with SLAs for IOPS, CPU and bandwidth. Cheap cloud offerings will not have any guarantee of performance. We pay a lot more for our private cloud but it is what we need.

To be clear - we are using a private cloud to host specific instances of an application for individual customers. It is not the typical scale-your-website-to-ten-thousand-servers scenario that drove the original Amazon concept or it touted in most of the vague cloud advertising.

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Thanks for that explanation. So, private cloud too is located outside my enterprise's premises, and here I get better priorities, better SLAs etc as compared with plain-cloud. Basically point-2 in Tangurena 's reply above . Is my understanding correct here ? –  Rangzy Jul 16 '11 at 18:03
    
Our private cloud is a set of computing resources but it is floating around somewhere in our providor's data center. As their hardware fails or is changed the private cloud will move around. Within that cloud we can create as many VMs as we want, overcommit CPU and memory as we want etc. My understanding of most public cloud offerings is you rent a machine and send the image that it boots and runs. If the machine fails then another instance will start. You are responsible for ensuring no work is lost. A private cloud can give you guaranteed local disk storage. HTH –  james Jul 16 '11 at 23:05
    
There has been computer hardware in the past where all of it was redundant. It isn't done these days because it was ridiculously expensive. I guess it may also have required techniques that needed very slow operating speeds, but wouldn't know that for sure. –  Donal Fellows Jan 27 '12 at 14:54

The concept of a cloud makes no specific mention of who owns it. Easily consider Microsoft writing an Azure application... is it still a cloud if they own it? Sure it is.

A private cloud is when you have a cloud environment that is hosted and maintained by you/your company. Some buzzwords kicking around for an alternate name (that might help your google searches) are 'cloud appliance'.

Here's Microsoft's Azure offering with respect to a private cloud, or cloud appliance.

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Definition of The Cloud is very broad, can mean IaaS (Infrastructure as a Service), PaaS (Platform as a Service) or SaaS (Software as a Service). But let's focus only on IaaS. Typically this means providing full stack virtual servers with automated provisioning, abstracting away the hardware and making services easily scalable. This doesn't mean that whoever is operating the data-center needs to be a separate commercial entity though.

There are two typical private cloud setups:

  • true Private Cloud, is a cloud which is operated entirely and exclusively by single entity for it's internal use;
  • Virtual Private Cloud, which is a portion of a public cloud firewalled from the rest of public and typically available via VPN.
  • hybrid Private Cloud, which is a hybrid of above two. This is useful for so called Cloud Bursting, in other words offloading short burst of computing to the public cloud. This way organization doesn't need to over-commit resources.
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Given the information on Rackspace's web site, this seems like the accurate answer. –  Brandon Oct 13 at 14:05

Virtual Private Cloud or Private Cloud can be defined as an integral part of a shared or public cloud. There prevail no changes in the eminent features, when compared to public or shared cloud network. In fact a Private Cloud network is rewarded with features like: better enterprise and customer control, enhanced security and no more tinkering issues related to regulatory compliance.

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You may find the following links as interesting reads, to get an understanding of PRIVATE CLOUD.

  1. Microsoft on what is Private Cloud?
  2. Rackspace on What Exactly is a Private Cloud?
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