Maybe explaining the below terms will be better than trying to come up with a technical definition of cloud Computing.
IaaS(Infrastructure as a Service)
IaaS provides data center, infrastructure hardware and software services over the web. One example is Amazon EC2. This is probably the most dominant form of Cloud Computing that we see today.
PaaS ( Platform as a Service)
PaaS is the next level of abstraction and provides the platform to build software services or products. For instance it may provide a Database, Web Server etc. Example is Salesforce.com's force.com.
SaaS (Software as a Service)
In SaaS, applications are provided as hosted services over the web.Probably the most widely used model of Cloud Computing.
So you could define Cloud Computing as "some service provided over the internet". It could be a computer server, a virtual server, a pre-configured OS, a hosted environment(Middleware), web based apps ( Google Apps), Web Services (Gmail ) etc. The three characteristics of a cloud service are:
- Elasticity
- Self-Service access
- Quick response.
Cloud Computing versus Grid Computing
Grid Computing typically relies on a batch scheduling mechanism to fan-out the task to multiple nodes and then accumulate the results. So Grid computing doesn't necessarily deal with getting processing capacity right now and instead focuses on some mechanism that is predefined and allows the "batch-job" to schedule jobs across these Grid nodes.
One could argue that Cloud Computing is more evolved version of Grid Computing, Virtualization is important for Cloud Computing because it is on-demand and is a key difference versus Grid Computing. However there are ways of achieving this by using Multi-Tenancy (Salesforce.com?) without Virtualization and we need to talk about those reference models.
If I haven't confused you already, then let me try some more. What about Grid Computing that is available in the Cloud? :-)
Public, Private, Hybrid and Community Clouds
Location is not important here but the ownership is. Who "owns" the facility? If the facility is shared by multiple public clients then it's a public cloud. If the facility is co-located within the enterprise ( it could be managed by a third party provider) then it's a private cloud. Hybrid clouds, ofcourse combine elements from both public and private clouds. Community clouds have multiple owners and are shared across those communities.
Cloud Computing benefits
Faster processing by making use of better/faster infrastructure available at much cheaper rates.
Minimize infrastructure bottlenecks by delegating the scalability and on-demand handling to the provider.
Low barrier to entry by allowing SMBs to participate in provinding solutions irrespective of the size of their data center.
In spite of the benefits, we do have to consider the network bandwidth requirements forced by servicing clients. Is it sufficient to meet the clients demands? What is the latency?
So, how do you use the Cloud?
OCCI is working towards standardizing the "API" to access the cloud but unfortunately, it is not completely implemented at vendors yet. Not sure if the major vendors like Amazon and SalesForce.com are part of it, so Customers hoping for interoperability between cloud providers will be disappointed. However it is still a useful resource to keep track of.
Architecture specific focus
Application architectures now have to consider a few extra things in addition to traditional issues such loose-coupling, distributed deployment. They now have to focus on delivering the entire application architecture as a set of composable services. If it can be virtualized, composed and assembled programmatically and quickly then it falls into the perfect category of Cloud applications.
The following are key for successful cloud applications:
Horizontal Scaling is the key to having a successful cloud application. If we can deploy the application components in a distributed fashion and provision additional deployments if the demand increases, we would be able to serve additional requests. Surge computing can be utilized as well to procure the computing needs from public clouds in case we are running in a private one. Horizontal scaling assumes we have Parallelization at some level. Without Parallelization, the nodes would depend on each other or on some other common service which would become the bottleneck.
Security, Compliance are important topics that we can't cover in detail in this post but should be handled in any cloud architecture. Concern or doubts regarding these two are perhaps the main reason why cloud is not adopted in large corporations. They deserve a separate and a detailed post.
IBM cloud reference architecture
Not sure how much detail I would be able to go into but the majority of "fluff" around the IBM cloud reference architecture can be ignored. Most enterprises don't embark on providing IaaS, PaaS and SaaS in the same breath. It's mostly a business decision and what makes economic sense. However, here is what you can take away from it:
Common Cloud Management Platform (CCMP) consists of Operational Support Services (OSS) and Business Support Services (BSS)
- Business Support Services represents the business-related services involving pricing, metering, billing, account etc
- Operational Support Services represents the technical-related services involving, provisioning, Ticket Management, Virtualization Management etc.
Qos (Quality of Service) in CCRA
The non-functional aspects like Security, Resiliency, Performance & Consumability are cross-cutting aspects of QoS spanning the hardware infrastructure and Cloud Services and must be viewed from an end-to-end perspective including the structure of CCRA by itself, the way the hardware infrastructure is set up (e.g., in terms of isolation, disaster recovery, etc.) and how the cloud services are implemented. The major aspects of QoS are:- Governance and Policy.
- Threat and Vulnerability Management
- Data Protection
- Availability & Continuity Management
- Ease of doing business
- Simplified Operations
Summary
- It's a starting point. If Cloud Architecture seems daunting then this is a good starting point.
- It's a good "best practices" document. It does define the collective experience of IBM experiences across various cloud solutions. There's got to be something useful here. :-)
- It does define four architectural principles(referred as ELEG) of which atleast three seem to of value.
- Efficiency. Basically means we need to increase utilization of cloud services.
- Lightweightness. Basically use some form of Virtualization or other technique to avoid "heavy" management of IT.
- Economies of Scale. The idea is to have common management services that can be shared across cloud flavors.
- Genericity. No clue what the message here was! Please read the document and help me! :-)
Three and Four seem similar and not sure what the differentiating factors are. Maybe we need to get some kind of context around the IBM doc to fully appreciate the message because it will come up in discussions and it will be important to explain the best points of this and avoid the unnecessary details. I think I will get back to this someday...
There are other Reference models out there. NIST has one and so does DMTF. Again, I will get to them someday... :-)
