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I'm looking into cloud hosting and came across the terms private cloud and public cloud. Are they the same as shared hosting vs. vps/dedicated hosting?

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up vote 2 down vote accepted

A similar concept, yes. But usage of the terms are a bit ephemeral.

A private cloud is one that is single-tenant. That is, your VMs run on hardware dedicated to the task, with no unrelated company sharing that tin. This may be for example a VMWare or Microsoft Virtual Infrastructure that you host and maintain, or it could be hosted by a third party but dedicated to your use. In theory there could still be an automated billing and provisioning system for this, but I don't know of a system that's active today that'll do fully automated provisioning yet dedicate your own piece of hardware.

A public cloud is shared infrastructure, multi-tenant environment. Your VMs may be executing on the same physical hardware as another client's VMs. In both cases your VMs and networks are still distinct units in their own right, it's just dedicated hardware vs shared tin.

So that's my yardstick, but it's not universally accepted. Off the top of my head you could also differentiate on the basis of availability - Anything home-rolled is a private cloud. Anything available to public via a web interface is a private cloud. But then what about business to business cloud solutions that aren't widely available? Likewise, you could divvy it up by network connections - Clouds connected back solely to your environment are private, and setups that can link straight out to the web are public. Even Wikipedia disagrees:

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OpenStack (specifically the Compute component) is aiming to provide the automated provisioning and management for private clouds. Eucalyptus has a similar goal. – MonkeeSage Aug 31 '11 at 15:38

It's about where the infrastructure running the cloud environment is hosted. In private clouds, all hardware is hosted within your company's data center(s) while the infrastructure in public clouds (like Amazon EC2) are hosted by another company and you use just the cloud environment.

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Depends on your perspective.

If you are talking about wanting to build a public cloud - you are talking offering cloud services to other (e.g. building your own EC2) If you are talking about building a private cloud, it's something that the services are only consumed by those within your organization, or perhaps only managed within your organization. (The resources might provide public facing services like websites) You would use something like CloudStack or Eucalyptus to build a cloud and offer those services internally.

If you are talking about consuming cloud services, the private cloud definition remains the essentially the same, but the public cloud definition changes to mean a service offered to by someone else, such as Amazon, Godaddy, etc.

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