Whether you think about virtualization of hardware or you already are in the virtualization, the main question is “How do I separate my individual systems?”.
This blog is comprised of 2 parts. This first part deals with the basic ideas behind virtualization and zoning, while the System Landscape planning with Global and Local Zones – Part 2 shows how to separate the individual systems that make up a SAP Business Suite 7 landscape onto different global and local zones.
Some thoughts ahead
I think it is ok, to spend a few lines on the basics. So I think we should take a look at some things first, before diving into how to separate an SAP Business Suite landscape:
- What is virtualization?
- What are zones, domains, partitions?
What is virtualization?
Wikipedia states that virtualization is a broad term in the computer industry that refers to the abstraction of computer resources. The part of the wikipedia article on virtualization (you can find it here) that is of most interest to us, is on virtual machines.
A virtual machine is a software implementation of a computer as opposed to standard hardware. That means, very simply put, a virtual machine makes your OS believe it has a standard hardware underneath, where in reality this hardware is emulated by some sort of software – this type of virtualization is called a system virtual machine.
There is a second kind of virtual machine, which not emulates a complete set of hardware – including processor and interupts and everything – but only those parts needed for a specific process. It is consequently called a process virtual machine.
The piece of software that is responsible for this “hardware emulation” is called the hypervizor (sometimes also referred to as virtual machine monitor).
The main advantages of virtualization are:
- multiple OS environments can co-exist on the same computer, in strong isolation from each other
- application provisioning, maintenance, high availability and disaster recovery can be setup much easier
- the virtual machine can provide a hardware environment in the virtual machine, that is different from that of the real machine
Of course, the first two points are the ones we are interested here.
The most common products for System Virtualization is VMWare (for Linux, Windows and Mac OS X) or Parallels for Mac OS X.
VMWare with their product VMWare ESX Server is certified to be used forproductive SAP installations and can be found on multiple customer sites.
What are zones, domains, partitions?
Zones, Domains or Partitions are all different words for nearly (but really only nearly) the same. It is a concept of providing distinct areas for the installation of an OS where these installations are separate instances of the underlying global operating system.
In this type of virtualization we typically don’t have the possibility to emulate a different hardware architecture in the VM, than that of the real underlying hardware. So it is, very very strictly speaking, not a real virtualization, but a system seperation – but let’s not split hairs here.
Zoning vs. System Virtual Machine
The idea behind zoning, as opposed to system virtual machines, is to provide independant computing environments in which we can install software that should be seperated from each other. – So far it’s the same idea. But, with Zoning there is a second plot to it. The independent zones inherit most of their OS infrastructure from the global operating system that instantiates them. That means, for example, the kernel of a Solaris 10 zone is inherited from the kernel of the upper global zone, from which it is started of.
Maybe a picture might help here:
What you see is this: a hardware box in which a hypervizor (here called the control domain) acts as a controller for different zones – called Global Zones. These global zones in turn provide multiple local zones and those are the individual OS environments in which we would install and operate our SAP instances.
- The big pink colored box represents the hardware machine – lets say a Primepower by SUN.
- The different CPU boards shown are system boards that bring their own CPU(s) and memory.
- The blue grey area on the left is the Control Domain – aka hypervisor – it needs it’s own CPU.
- The green areas are all different global zones – controlled and separated by the control domain.
- The blue boxes are the individual global Solaris 10 installations within a global zone – it can provide file systems, kernel and services to it’s own local zones.
- The inner areas (differently colored) finally represent the local zones, with a local installation of Solaris, where all client application run – independently of each other.
As you can see, a global zone can either be pinned to a specific CPU, or it can traverse CPU (and thus memory boards). Consequently the inner global OS can have more or less computing power and this of course also holds true for the local zones.
Zoning, as we’ve seen is a concept a bit different to System Virtualization. Bothconcepts provide an architecture where one can create separate computing areas in which a client OS and on top of that applications can be installed. But where a System Virtual Machine typically provides a more less complete hardware emulation, with zoning we can make nearly direct use of the uunderlying hardware.
So what is Logical Partitioning, or the Domain Concept (as found for example in Linux environments)? Those names refer to the same concept (more or less) as zoning – providing different execution environments on a common shared hardware without the need to simulate or emulate a complete processor set.
The advantage is a much higher speed gain opposed to System Virtualization. This advantage comes from the fact, that we don’t need to emulate the hardware in a software environment, but have controlled, but direct access and thus the full power of it.
The disadvantage is of course, we cannot provide an operating system version or hardware architecture, which is different from that of the box we run on or the installed global operating system.
In my next post in this series, I will show you how to use Zoning to separate a typical SAP Business Suite 7 landscape.