Elements of Cloud Strategy
Service Model : IaaS, PaaS, SaaS
Delivery Model : Public and Private
To get a clearer understanding on Cloud Layers :
The items on the Left are things that gives you more control to realize your solution whereas on the Right are Solutions that somebody else has well thought about and come up with.
Problems will always exist and they slowly move from IaaS towards SaaS over time and hence these layers will remain commodities to follow as a lifecycle.
Benefits of different Service Models
SaaS is the ultimate commoditization of well-understood software problems, but poorly suited to bespoke or other custom needs
PaaS is the ideal cloud environment for rapid development of bespoke software systems that require nothing specific from the underlying infrastructure; the focus is on apps. Poorly suited for regulatory and other compliance or any but the simplest infrastructure needs.
IaaS provides maximum control over the infrastructure without the need to worry about the infrastructure; well suited to complex custom software systems. Network and storage I/O can be a challenge for IaaS.
1.Public Clouds is a multi-tenant cloud infrastructure delivered by a provider that has achieved scale (IaaS, PaaS and SaaS) – For the greatest level of agility.
2.Private Clouds is a single tenant virtualized infrastructure with consumption characteristics similar to a public cloud (IaaS and SaaS) – For greater control for regulatory, compliance or bespoke requirements – Its isnt really a cloud at all, it has heavy capacity constraints.
[Multi-tenancy is an architecture in which a single instance of a software application serves multiple customers. Each customer is called a tenant.]
Private cloud has more transparency (because user knows what is exactly available rather than to make him believe what is made available to him.) The user gets a privileged access to the infrastructure than a user of Public Cloud gets. Virtualization itself is not private cloud, in addition to that we need a platform like eucalyptus, openstack, cloudstack, joyent etc.