In my previous article, I discussed the basic concepts behind Cloud Computing including definitions, characteristics, and various service models. In this article I will discuss service models in more detail, and in particular the comparison between IAAS and PAAS from a developer’s standpoint.

I’m using two giant cloud players for illustrative purposes: Amazon Web Service representing IAAS and Windows Azure Platform representing PAAS. Nonetheless, please be informed that the emphasis is on the service models and not the actual cloud players.

Figure 1: IAAS VS PAAS

Infrastructure as a Service (IAAS)

IAAS refers to the cloud service model that provides on-demand infrastructure services to the customer. The infrastructure may refer to rentable resources such as computation power, storage, load-balancer, and etc.

As you can see on the left-hand side of Table 1, the IAAS provider will be responsible for managing physical resources, for example network, servers, and clustered machines. Additionally, they typically will also manage virtualization technology enabling customers to run VMs (virtual machines). When it comes to the Operating System (OS), it is often arguable whether it’s managed by the provider or customer. In most cases, the IAAS provider will be responsible for customer VM Images with a preloaded OS but the customer will need to subsequently manage it. Using AWS as an example, AMI (Amazon Machine Image) offers customers several types of Operating Systems such as Windows Server, Linux SUSE, andLinux Red Hat. Although the OS is preloaded, AWS will not maintain or update it.

Other stacks of software including middleware (such as IIS, Tomcat, Caching Services), runtime (JRE and .NET Framework), and databases (SQL Server, Oracle, MySQL) are normally not provided in the VM Image. That’s because the IAAS provider won’t know and won’t care what customers are going to do with the VM. Customers are responsible for taking care of them. When all of the above mentioned software has been settled, customers will finally deploy the application and data on the VM.

Step-by-step: Setting-up an Application on IAAS Environment

To convey a comprehensive explanation, I am going to illustrate the steps involved when setting up an application in an IAAS environment. For that, I’m borrowing a slide from a presentation by Mark Russinovich, at the BUILD conference. This illustration explains how a typical IAAS provisioning model works.

Figure 2: Setting up an App

Considering a common scenario when you have finished developing a multi-tier application, you as the developer will need to deploy it to the cloud. The application will need to be hosted on a Web Server and an RDBMS database. For IAAS, here are the typical steps:

1.       Preparing Database Servers

Select the VM Images from the VM Images library. The VM Image will then get provisioned and launched. If DBMS software is not provided, you will need to install DBMS on your own.

2.       Preparing Web / Application Servers

Select VM Images from the library to get provisioned and launched. If the web/app server/runtime aren’t installed, you’ll need to install them by yourself.

3.       Provisioning a Database and Its Objects

The next step is about provisioning the database, including configuring the data files, log files, security, etc. Then you create the tables and add data to it.

4.       Deploying Your Application

Next you take the application that you’ve developed and deploy it to the Web Server.

5.       Configuring load-balancer

When you need to host your application on multiple instances, you may also need to configure things such as the IP Address for each instance and load balancer.

6.       Managing Your VMs and DMBS

The final step is about managing the VMs. For example, when there’s an update or service pack on the OS, the IAAS provider will not automatically do it for you. Instead, you may need to do it by yourself.

Platform as a Service (PAAS)

Now, let’s jump into another cloud spectrum, “PAAS”, to see how it differs. In PAAS, the provisioning model is about an on-demand application hosting environment. Not only managing the component like an IAAS provider would, a PAAS provider will also help customers manage additional responsibilities such as OS, Middleware, Runtime, and even Databases, as can be seen on the right-hand side of  Table 1.

In other words, you can think of PAAS as renting a stack of software, hardware, and infrastructure. Customer will just need to bring the application and data and they are ready to go.

Step-by-step: Setting-up an Application on PAAS Environment

For PAAS, given that the database server, VM, and web server VM are readily provisioned, you just need to do two steps, as illustrated by another slide from Mark Russinovich.

Figure 3: Provision and Deploy

1.       Database Provisioning

You might need to indicate where (which region) your virtual DB Server is provisioned, but you don’t have to install a bunch of DBMS software on your own. You will need to provision the database, create tables, and add data.

2.       Deploying Your Application

This is a similar step applicable to IAAS, you will still need to deploy your application on the PAAS cloud environment.

How about the load-balancer? Take Windows Azure as example, it will all automatically be configured and ready to take the traffic, and everything else will be automatically managed. You don’t have to worry about IP Addresses or a load-balancer.

How about maintaining VMs? The DBMS and Web Server VM will be maintained by the provider. For example:

• If the VM where your application is hosted has any hardware issues, the provider should be able to detect the failure and rectify it immediately to make sure that your application will stay up and running. In Windows Azure, Fabric Controller will be the component handling these kinds of issues.
• If there are new updates or patches on the Operating System, the provider will make sure that the VM your application sits on is always updated. For example: Windows Azure uses “Guest OS Version” to differentiate service updates. Of course you can also choose to stick to one version or auto-update.

Figure 4: Configuration

Summary

To summarize, we have investigated different service models and provisioning steps of IAAS and PAAS solutions. PAAS providers indeed take on much more responsibility for your solution than an IAAS provider would. On the other side, IAAS may offer more flexibility at lower level (example: public IP addresses, load-balancer, etc.).

There’s no one-size-fits-all here. As a developer or architect, you should understand a customer’s need and determine the correct model to get the best possible outcome.

This post was also published at A Cloud Place blog.

Introduction

I’m aware that there many cloud computing introductory articles or papers out there, so why am I writing another one? As this my first article at A Cloudy Place, I’d like to start at the beginning and take a new approach to explain the cloud.

Would you rather buy or rent a car?

The analogy that I will be using is very simple and I believe some readers have probably run into it at some point. Have you ever considered buying or renting a car?

Buy Your Own Car

Buying a car is a big investment, and there are a lot of important decisions to take into account. Some people like all the different options, and others don’t want to bother with thousands of decisions.  When buying a car you have full control over everything, its make and model, cost, interior, etc. Additionally, you’ve got to work about taxes, insurance, inspections, and all sorts of maintenance, you’ve got the control, but it comes with a hassle.

Renting a Car

Then how about renting a car? You have fewer and simpler decisions to make. You just need to select a car from what’s available, and you can switch your car if something comes up.

Rent when you need; pay when you use. You don’t have to worry about maintenance costs, tax, and insurance since they are included in your rental fee. On the other hand, there are obviously some disadvantages. You’re limited by what’s available from the rental vendor, you may not be allowed to customize the car, and the car is not dedicated to you all the time.

Translating the Analogy to Cloud Computing

This simple real life analogy is easily translatable to Cloud Computing.

Buying your own car is similar to setting up your own on-premise data center. You have the flexibility to customize whatever you like, starting from physical infrastructure, the security system, hardware and software, etc. However, you also have to invest a lot of money upfront. And also, you will also need to manage it later when it’s operating.

On the other hand, instead of building your own data center, you can rent computation power and storage from the cloud provider. You can scale in and out when necessary. Just pay when you use. No specific commitment takes place. You can start and stop anytime.

Characteristics of Cloud Computing

This summarizes the characteristics of cloud computing.

• On-demand

Resources should be always available when you need them, and you have control over turning them on or off to ensure there’s no lack of resource or wastage happen.

• Scalable

You should be able to scale (increase or decrease the resource) when necessary. The cloud providers should have sufficient capacity to meet customer’s needs.

• Multi-tenant

Sometimes you may be sharing the same resource (e.g. hardware) with another tenant. But of course, this is transparent to the customer. Cloud provider shall responsible the security aspect, ensuring that one tenant won’t be able to access other’s data.

• Self-service computation and storage resource

Related processes including: billing, resource provisioning, and deployment should be self-service and automated, involving much less manual processing. If a machine where our service is hosted fails, the cloud provider should be able to failover our service immediately.

• Reliability

Cloud provider should be able to provide customer reliability service, committing to uptimes of their service.

• Utility-based subscription

You will pay the cloud provider as a utility based subscription, just like paying your electricity bill – without any upfront investment.

Cloud Computing Service Model

Cloud Computing consists of several type of service models.

• On-premise Environment
  As you can see, for the first stack from left, you will need to take care of everything from networking all the way up to applications. This is typically what many of us are doing today.

• IaaS (Infrastructure as a Service)
  IaaS helps you to take care of some of the components, starting from networking to provisioning the OS. But you are responsible for the middleware, runtime, data, and application. Sometimes IaaS vendors will just provide the OS but will not manage updates or patches for you. You basically just rent the virtual machine (VM) with the preferred OS installed. They won’t care what you do with the VM.
  Example of IaaS market players: Amazon Web Service, Rackspace, and VMware vCloud.

• PaaS (Platform as a Service)
  Paas is one level up from IaaS, where cloud providers not only take care of the components that IaaS does; but also manage the platform-level components like middleware and runtime. Middleware such as applications / web server (IIS, JBoss, Tomcat, etc.) and runtime (.NET Framework, Java runtime) will be pre-installed. As a customer, you just need to focus on managing application and data.
  Example of PaaS market player: Google AppEngine, Windows Azure Platform, andforce.com.

• SaaS (Software as a Service)
  SaaS is probably the most common one as we may have been using it, unaware that they are actually cloud services. SaaS takes care of all the stacks from networking to application level. You don’t even manage the application and data storage. All you need to do is to use the system.
  Example of SaaS market player: GMail, Office 365, and Google Docs.

Cloud Computing Deployment Model

There are three main cloud deployment models, each on with its own set of customers it’s targeting.

• Public Cloud
  Public cloud provider refers to the cloud platform that targets any types of customers, regardless of whether they’re an independent consumer, enterprise, or even public sector. Normally, public cloud providers are considered prominent players which have invested huge amount of capital. Windows Azure Platform by Microsoft, AWS by Amazon, AppEngine and Gmail by Google, etc. are all examples of public cloud services. Customers who possess sensitive data and application normally do not feel comfortable using public cloud due to privacy, policy, and security concerns. Remember, for public cloud, the application and data will be stored in the provider’s data center.

• Private Cloud
  Private cloud is infrastructure that’s hosted internally, targeting specific customers or sometimes exclusively within an organization. Setting up a private cloud is normally more affordable when compared to a public cloud. As the matter of fact, there are many organizations who have implemented their own private cloud system with product offering from vendors such as IBM, HP, Microsoft, and so on. Customers who possess sensitive data and application feel more comfortable going with this approach since the data and application are hosted privately.

• Hybrid Cloud
  Hybrid cloud is the combination of public and private clouds, or sometimes on-premise services. Customers who look into this solution generally want to utilize the scalability and cost-competitiveness that public cloud providers offer, but also want to retain their sensitive data on-premise or in a private cloud. With the benefits derived from both deployment models, the hybrid model solution has become more popular nowadays.

I sincerely hope that, this article would be helpful to you. In my next article, I’ll discuss more about the comparison between IaaS and PaaS.

This post was also published at A Cloud Place blog.

I am glad to share that “a cloudy place” blog is finally up here: http://acloudyplace.com

What is “a cloudy place”?

A centralized blog focused on cloud technology exclusively for developers. If you’ve heard about SQL Server Central, it’s somewhat similar but focus on cloud computing. You can find topics such as general cloud info, Amazon Web Services, Windows Azure, and so many more.

Who own “a cloudy place”?

“a cloudy place” is owned and managed by Red Gate, a software company specializing in SQL, DBA, .NET, and Oracle development tools based in Cambridge, UK.

What to do with me?

Aha! I am invited to become a contributor on “a cloudy place”. In a first few post, you will see me write about some generic cloud concept. Of course, I’ll discuss more about Windows Azure later on.

You can find my articles here.

Happy “cloudy” reading on “a cloudy place”!