Just
finished a 20 part OpenStack Series on my blog. May be it is a good idea to step back to take
a look at what a cloud is.
According
to NIST (National Institute of Standards and Technology) publication 800-145,
Cloud Computing is defined as “a model for enabling
ubiquitous, convenient, on-demand network access to a shared pool of
configurable computing resources (e.g. networks, servers, storage, applications
and services) that can be rapidly provisioned and released with minimal
management effort or service provider interaction.”
This
document further defines that a cloud computing has 3 service model and 4
deployment model and 5 essential characteristics.
Wow,
it is so theoretical. Who want to
memorize these definitions? I am not taking
any certification exam from NIST.
But
when I read what they are I find that these service models, deployment models
and essential characteristics are being used widely in all the cloud related
articles. Let’s take a quick look and see if you agree.
Cloud
Service Model
- Software as a Service (SaaS)
- Platform as a Service (PaaS)
- Infrastructure as a Service (Iaas)
Every
day we some form of Software as a Service.
Most people use Yahoo Mail or Gmail.
Microsoft Office 365 is another form of SaaS. User of SaaS only interfaces with the
application and do not know what and how it is being supported. You may be surprised to know Facebook is a
form of SaaS.
I
think the best way to describe Platform as a Server is that user is responsible
for the application and data that is associated with it. The hardware, OS, network and storage is
hided from the user. AWS Elastic
Beanstalk, Google App Engine and RedHat’s OpenShift are good example of PaaS. In this model the OS license is not a concern
of the user even Linux is free there is no need to worry about when to apply
the latest security patches or have to schedule down time. The development or production platform is
just there to be consumed. The PaaS
provider will take care of providing a platform according to the SLA.
Infrastructure
as a Service will provide all the hardware for compute, network and storage
including the hypervisor and use is responsible for maintenance and security
patches of the Operating System that is running on the infrastructure. Software license is a big consideration in
this model.
This diagram
best describe the 3 cloud service model the modules in green are the
responsibility of the user and the modules in grey is the responsibility of the
provider. (A picture is worth a thousand words).
Image source: http://venturebeat.files.wordpress.com/2011/11/iaas-paas-saas.jpg
Here
is a good article
that compares the 3 service model.
Cloud
Deployment Model
- Private Cloud
- Community Cloud
- Public Cloud
- Hybrid Cloud
I believe
every heard of private, public and hybrid cloud. Community cloud is for exclusive use by a
community and can be hosted on or off premises.
I would think soon we will have a Personal Cloud add to the list. The main difference between private and
public cloud is whether the cloud is hosted on or off premises.
For Public
cloud everyone knows about Amazon Web Services and Google Compute Engine and
lately Microsoft Azure. And for private
cloud OpenStack is a hot topic and yet I don’t think it is being deployed as
wide as its publicity.
I see lots
of potential in the use of Hybrid cloud and VMware rebrand vCloud Hybrid
Service into VMware vCloud Air and is promoting a complete cloud solution.
Image source: https://communities.vmware.com/servlet/JiveServlet/showImage/38-6265-10766/cloud_roadmap.png
Cloud
Essential Characteristics
The
essential characteristics defined by NIST are
- On-demand self-service
- Broad network access
- Resource pooling
- Rapid elasticity
- Measured service
These
are all self explanatory. Amazon Web
Services has CloudWatch for monitoring and since it is a paid service, billing
is of course has to be in place.
OpenStack is catching up on this with the Ceilometer but on the billing side,
it is only taking care of the measurement portion. A complete billing system is not in place for
OpenStack
Reference:
(Csd), Nist Computer Security Division. NIST SP 800-145, The NIST Definition of Cloud Computing (n.d.): n. pag. Web.
(Csd), Nist Computer Security Division. NIST SP 800-145, The NIST Definition of Cloud Computing (n.d.): n. pag. Web.
