PaaS vs IaaS vs SaaS

Sirkassad · February 2017

So I am reading through some sample questions from Eleventh Hour and one of them has me confused. I am assuming that since this question appears in a book I can re-post without violating anything. It truly has me second guessing my understanding of the types of cloud services offered.

What is the cloud service level if Linux hosting is offered?

So here is my thought process...the way I learned to differentiate between the three is what the cloud service provider provides, and what is left to the customer to provide.
Here is the definition of the three:

The most common cloud service models are
• Infrastructure as a Service (IaaS) Cloud providers offer the infrastructure environment of a traditional data center in an on-demand delivery method. Companies deploy their own operating systems, applications, and software onto this provided infrastructure and are responsible for maintaining them.
• Platform as a Service (PaaS) Cloud providers deliver a computing platform, which can include an operating system, database, and web server as a holistic execution environment. Where IaaS is the “raw IT network,” PaaS is the software environment that runs on top of the IT network.
• Software as a Service (SaaS) Provider gives users access to specific application software (CRM, e-mail, games). The provider gives the customers networkbased access to a single copy of an application created specifically for SaaS
distribution and use.

*Feel free to stop here and come up with your answer before reading on*

So given those definitions, my thought process was "In an IaaS the cloud provider does NOT provide the O/S, it is the responsibility of the customer (company), so I will rule out IaaS". In SaaS the provider provides the O/S and the application software the customer will need for its business.
The question only states the cloud provider will be providing a Linux host so I am reading this to mean that the customer is only getting a Linux host (Operating system, no applications). Easy-peasy, the answer is PaaS..

NO!!. Apparently providing a Linux host does not constitute providing an operating system (who knew Linux wasn't thought of as an operating system, according to google Linux OS is an open source operating system.) It also doesn't count as a software environment. So Linux is neither an operating system, or software..

So the correct answer, according to the book, is IaaS because a linux host apparently doesn't count as being a platform.

signumfidei · February 2017

The way I think of this is around the seperatation of responsibilities.

In IaaS - the provider gives you the infrastructure. They may give you the OS, or you may use your own image. You will be able to configure the OS as you please and completely break it if you want. As you manage the OS they give you - then its IaaS

In PaaS - probably the easiest examples are AWS RDS or Azures SQL. You are given a database platform, and your simply bring your own database files. You are not responsible for the OS (and have no access to it) and you have limited access to the DB platform.
Other more modern PaaS could be something like AWS Elastic Beanstalk - where you bring your java app, and AWS provide the IaaS layer, and the OS, Middleware and Runtime.

In SaaS - think of something like Facebook. You simply use the service.

cyberguypr · February 2017

When this type of confusion arises you need to check standards and frameworks. NIST 800-145 says that:

Infrastructure as a Service (IaaS). The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components (e.g., host firewalls).

Also, remember that with PaaS you get the FULL stack, or as you mentioned, a "holistic execution environment", not just the OS.

paul78 · February 2017

Another way that I think of it is who the target user is -

IaaS - end-user is a system administrator or a network administrator. Example - AWS EC2 or S3
PaaS - end-user is typically a software engineer or developer. Example - AWS SQS
SaaS - end-user is typically a business user or consumer. Example - AWS Workmail

iBrokeIT · February 2017

I prefer the "pizza as a service" analogy since who doesn't love pizza?!?

Aaronsmity · February 2017

To add to what others have posted:

In regards to the CISSP test I would assume the questions around them would be security-centric so how I understand it:
IaaS - purchaser is responsible for all security for whatever platform/application/software purchaser installs on it
PaaS - provider is only responsible for security of the platform provided, purchaser would be responsible for security of any applications installed on the platform.
SaaS - provider is responsible for all security

so PaaS and SaaS you need to make sure you understand that some or all security is out of your hands so contracts/SLAs/SOC2 Audits need to be reviewed to ensure security is addressed appropriately. in IaaS you need to be aware that your own processes need to provide the security.

TheFORCE · February 2017

This is a trick question and has to do with your understanding of what each service includes. The key term on the question is "linux host" what they are reffering to with that is not the Linux distribution or OS. You are assuming that they are referring to a distribution. When in fact they are referring to the hardware components of a host. Basically they are telling you that they will give you the infrastructure that can run a linux distro, they are not saying which distro. That would be something that you can setup.
As an example, consider this... we will give you a windows host. You can install any windows OS you want and you are guaranteed that it will work on that Windows host. Same thing with the question for Linux.

OctalDump · February 2017

"Offers" Linux hosting. So maybe they offer (support) a range of OS's and you can choose to run Linux. That is "Hey, we can host your Linux environment", which is pretty much what IaaS is. It's pretty close to how AWS works - the customer chooses an OS to run.

Well, at least that's a way to read the question so that the answer makes more sense.

Sirkassad · February 2017

TheFORCE wrote: »

This is a trick question and has to do with your understanding of what each service includes. The key term on the question is "linux host" what they are reffering to with that is not the Linux distribution or OS. You are assuming that they are referring to a distribution. When in fact they are referring to the hardware components of a host. Basically they are telling you that they will give you the infrastructure that can run a linux distro, they are not saying which distro. That would be something that you can setup.
As an example, consider this... we will give you a windows host. You can install any windows OS you want and you are guaranteed that it will work on that Windows host. Same thing with the question for Linux.

I have two things to say with regard to this reply..

First, I think you are correct in your assessment.
Second, that makes this a really stupid question

I say that because I am not aware of any major difference in HW for a 'Windows Host' vs a 'Linux Host'. In other words, telling me that you are giving me a Linux Host tells me nothing different than if you told me you are giving me a Windows Host. I can put a Linux distro on the same hardware as I can a Windows OS. To me this question isn't trying to see if you know the difference between an IaaS and a PaaS, which should be the goal of this type of Cloud computing question. instead it is trying to trick you, which should not be the goal of questions. Hence, why you called it a trick question...

I can only hope that there aren't actual test questions like this on the real exam

cledford3 · February 2017

Pizza as a Service - this is brilliant!

Thanks

Dakinggamer87 · February 2017

Great analogy using pizza

uleghari007@gmail.com · February 2017

Very good explanation in terms of security.

PaaS vs IaaS vs SaaS

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