Server Consolidation & Virtualization

Virtualization and server consolidation are the hottest buzzwords in the

industry today. The interesting thing is that virtualization used to be one of

the techniques for doing server consolidation. Today, virtualization can be used

for more than just server consolidation. It can be used for disaster recovery

and business continuity, testing and training, securing desktop environments,

and much more. Similarly, virtualization isn't the only technique for doing

server consolidation. Here, we'll look at the technologies in each area in

more detail.

Let's look at server consolidation first. The most common definition of

server consolidation is that it reduces the number of servers that you have in

your data center and other offices by moving the Operating Systems and

applications that were running on them onto a fewer, more powerful servers. This

is done with the objective of reducing administrative and management costs of

your existing fleet of servers. But that's not the only definition for it.

According to Gartner, server consolidation can be divided into three types:

logical consolidation, physical consolidation and rationalized consolidation.

There are vendors who have also categorized server consolidation differently.

IBM for instance, divides server consolidation into centralization, physical

consolidation, data integration, and application integration. In all cases, the

objective is to simplify your server infrastructure. Here, we'll go by Gartner's

definition.

Logical consolidation



This is about what most IT managers dread the most: documentation. How well
documented are the servers in your organization? Do you know which server is

located where, its configuration, how well is it utilized, and what applications

is it running? If you do, then you've already achieved one part of logical

consolidation. The other part is to understand how to use this information

effectively to plan your next server upgrade or purchase better, or improve

troubleshooting.

Physical consolidation



This is nothing but reducing the number of physical server sites that you have
by moving servers from those locations into a fewer locations. By doing this,

you can save not only the cost of maintaining so many servers, but you also save

on real estate costs.

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Rational consolidation



This is the most commonly known part of server consolidation, and the most
complex. It dramatically improves server utilization, but you must also have

failover support, as doing this is like putting all your eggs in one basket. In

this technique, you either put multiple applications onto a single Operating

System on one server, or you install multiple Operating Systems on a single

Operating System on the server, and then install applications on top of each OS

instance. Gartner calls the former technique as Workload consolidation and the

latter as partitioning. Workload consolidation needs a robust scheduler that can

balance the hardware resources amongst different applications. There are two

different ways of doing workload scheduling-processor binding and software

based resource allocation. In the former, different applications are tied to

different processors in a multi-processor machine. IBM's AIX Operating System

for instance can force processor affinity through a 'bindprocessor' command.

IBM defines processor affinity as the probability of dispatching a thread to a

processor that was previously executing it. HP also allows this on its HP-UX

processor using its HP-UXi 11i OS. In Software-based resource allocation, the OS

itself tries to allocate the hardware resources to the applications.

Server Consolidation using Partitioning



Partitioning is another way of doing server consolidation. You can do it at the
hardware level, which basically means allotting processor(s) and memory to

specific applications. This technique is a fairly old one and has been around in

mainframes and the UNIX world for a long time. It's only done on multi-CPU

servers, and physical hardware is used to create partitions on the server. Each

partition can thus have one or more CPUs, dedicated memory and I/O components.

These are electronically isolated and therefore are completely safe from each

other. Even if one partition goes down, the other partitions remain unaffected.

Another form of hardware partitioning can be achieved with blade servers.

They offer electronic isolation, and each server blade contains its own CPUs,

memory, and hard drive. The good news about blade servers is that their costs

have come down significantly.

The second type of partitioning is logical partitioning. This adds a firmware

to the hardware for doing the partitioning. IBM for instance, adds a firmware

hypervisor function in its pSeries servers that does virtual memory management,

debugs registry and memory access, and provides virtual tty support. The benefit

of logical partitioning is that you can alter resources to virtual partitions

without stopping the OS. The last form of portioning technology is called

software partitioning. This allows one Operating System to run several guest

Operating Systems on top of it. In other words, there's a hypervisor on top of

the host OS on the server, which allows multiple instances of an OS to run on

top of it. In case you haven't figured it out, then this technique is also

known as virtualization. Today, virtualization is one of the most happening

technologies and has moved far beyond being a mere technique for doing server

consolidation. Let's get dig deeper into it.

Understanding Virtualization



Many of the techniques we've discussed in server consolidation are a form of
virtualization, and they've existed in the UNIX world for ages. What's

relatively new is the introduction of virtualization technology on the x86

platform.

This is good because the real challenge of server proliferation has happened

in this segment only. Most organizations have tons of x86 based servers, the

result of which is high administrative overheads and operating costs, challenges

in managing the server fleet, etc. In fact, there are many studies which

indicate that most servers in the enterprises are not utilized beyond 15-20% of

their actual capacity. This wastes a lot of compute power. It wastes a lot of

precious energy that powers up servers and keeps them cool. Virtualization can

improve server utilization by deploying more than one Operating System and

applications on single server. It achieves not only server consolidation, but

also improves resource utilization, reduces real estate requirement in a data

center, and lowers energy requirements. Moreover, virtualization technology on

the x86 platform is also available for desktops.

Types of virtualization



The oldest type of virtualization is emulation, which is running an OS that's
meant to be run on one platform on another platform. The one that's gained

popularity today is native virtualization, which allows you to run multiple

Operating Systems on same platform. The difference here is that it doesn't let

you run Operating Systems for some other CPU. Another form of virtualization is

called paravirtualization, which also let's you run multiple Operating Systems

on the same system, with the difference that it's tuned to provide better

interaction with the CPU, memory, and other I/O devices. It also interacts

directly with Intel's VT and AMD V technologies to give better performance.

Hardware Assisted Virtualization



The dark side of software virtualization on the x86 platform is that performance
takes a hit as the number of virtual machines increases. To tackle this, Intel

and AMD are coming out with virtualization technology in their processors. Intel

calls it Intel VT, while AMD calls it AMD V (code name



Pacifica).

Intel VT



This was officially launched in 2005 and was available in most Pentium 4 6x2,
Pentium D 9x0, Xeon 3xxx/5xxx/7xxx, Core Duo and Core 2 Duo processors. The

technology facilitates a CPU to act as if it were numerous CPUs working in

parallel. It has some extra instruction sets that are used in virtual machine

emulation. These instruction sets reduce the communication process between

virtual machines and actual hardware, which was earlier performed by VMM. This

eliminates overhead and improves performance.

AMD-V



AMD introduced its virtualization extension in its 64-bit architecture in mid of
August 2006. This technology uses Direct Connect Architecture, which provides a

balanced mechanism to support virtualization software in managing, partitioning,

and securing I/O devices. This is done for improved performance and less

implementation complexity in providing I/O in virtual environments. It helps

eliminate bottlenecks inherent in FSB architectures and gives high-throughput

responsiveness and scalability for your applications to improve overall system

efficiency. Right now this technology is available in AMD Opteron Processors.

Virtual Appliances



This is the latest feather in virtualization technology's cap. Simply
speaking, it is a combination of OS and application. Instead of distributing

apps alone, ISVs can bundle an optimized OS with them. The virtual appliance

would then simply be dropped on top of a virtual infrastructure from some

vendor, and would be ready to run.

This would save IT managers the trouble of first installing an OS on a

hardware, and then installing and customizing the application. They can instead

focus straightaway on configuring and customizing the application as per their

organization's need. It's a fairly powerful concept, and is worth watching

out for.