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Server Update 2006

The emergence of virtual server ecosystems

Virtualisation is a concept that has spread across IT infrastructure in aspects such as servers, storage and networks. Server virtualisation has matured to the point where its benefits outweigh the costs. By Anil Patrick R.

The concept of virtualisation holds much promise if executed right. This is more so in terms of server virtualisation since the costs involved are marginal when compared to the benefits that can be derived.

Naveen Mishra

Senior Analyst
Server Markets
Gartner India

“Virtualisation on the x86 (and x86-64) server platforms is a trend that is being discussed and evaluated today in many organisations. This is one trend which is going to remain for quite a while in the industry,” opines Naveen Mishra, Senior Analyst, Server Markets, Gartner India. So it will be more accurate to say that 2006 will be the year when Indian organisations start experimenting with and adopting x86 based server virtualisation.

The growing trend of virtualisation on the x86 platform is also substantiated by Gartner’s Top Ten Trends and Predictions for 2006. According to the report, virtualisation will drive the need for Real Time Infrastructure (RTI) in the APAC region. To cope with the increasing volume and velocity of information, organisations will need to adopt RTI which relies extensively on virtualisation. The technology can improve IT resource utilisation and increase flexibility in adapting to changing requirements and workload. With the addition of service-level, policy-based automation, virtualisation leads to RTI, according to Gartner.

Starting a long journey

The concept of server virtualisation basically means that it is possible to simultaneously run multiple instances of the same operating system or several operating systems on a single server.

Considering that RISC boxes have had virtualisation capacities for many a year now, virtualisation is not a ground-breaking proposition as such. However, it has been virtualisation on the x86 platform that has given the concept more widespread appeal than its erstwhile RISC associations. “Virtualisation is the abstracting of the software from the underlying implementation. Server virtualisation has been around for decades now, and it is a mature technology,” comments Prakash Advani, Linux Practice Head, Novell India.

2006 will be the year when server virtualisation on x86 and x86-64-based servers will start to be accepted by the Indian enterprise. By ‘will start to be accepted’ we mean the start of a trend that will last for a long time.

x86 servers get virtualised

This approach of optimally using underlying hardware has several advantages, as we shall soon see. First of all, the price-performance ratio has improved tremendously on the x86 platform over the years. This is one of the reasons why server virtualisation has become a very viable proposition today for enterprises.

Advantages such as having multiple operating systems on a single server, easier management, higher optimisation and better DR provide a strong value proposition for medium-to-large organisations

Some of the other benefits of virtualisation include improved server utilisation, efficiency and manageability. Better server utilisation reduces the cost of hardware and manageability, thereby reducing the overall TCO. The ability to migrate virtual servers from one virtual environment to another without considerable difficulty provides easier management and DR capabilities as well. “Advantages such as having multiple operating systems on a single server, easier management, higher optimisation and better DR provide a strong value proposition for medium-to-large organisations. Virtualisation’s adoption will mainly be in large organisations, data centres and other large implementations,” says Mishra.

On top of this, 2006 will see many vendors offering new as well as considerably enhanced server virtualisation solutions (both hardware and software). Club the value propositions of x86 virtualisation with more maturity in the virtualisation space and it is clearly evident that 2006 will see considerable adoption in the enterprise.

What has changed now is that there is no need for proprietary or expensive technology to take advantage of it. “Virtualisation, which was earlier available only on high-end systems, is now available on commodity hardware, which means everyone can now take advantage of it,” Advani points out. Adds Mishra, “Today, virtualisation can be mainly classified into hardware and software-based optimisation. Each approach has its pros and cons, so selection has to be done based on the specific requirements.”

One way or another

There are basically two types of server virtualisation approaches in use today. The first one requires a host OS to run virtual machines (VM) on top of it. The second approach, known the ‘hypervisor’ or bare metal approach, makes use of an abstraction layer run between the OS instances and the hardware.

In the hosted OS approach, the virtualised server OS instances are run on top of the host OS. The virtualisation solution is installed as an application on top of the host OS. This approach relies on the host OS for all interfacing between the virtual machines and the server hardware. Microsoft Virtual Server 2005 R2 is an example of the hosted OS virtualisation approach.

On the other hand, solutions using the hypervisor (also known as the virtual machine monitor) approach are meant to be installed directly on top of the server hardware without the need for a host OS. In this type of server virtualisation, the hypervisor creates the interface through which the VMs interface with the hardware. Server OSs are created inside VMs or ‘containers’ created on top of the hypervisor.

The hypervisor is basically a software layer that includes a virtual machine scheduler to coordinate VM functioning. Hypervisors primarily assist in memory management and I/O virtualisation. VMware ESX server and the open source Xen Enterprise are examples of solutions using this approach.

What virtualisation is not
While virtualisation can provide many advantages, there are still many issues to be sorted out. The first is the lack of standards, but vendors are working on it.
The next is the issue of performance for high I/O applications. When running software virtualisation, applications that need fast I/O access (like databases and graphical applications) can face issues such as memory and virtualised processor / video card limitations, as well as scalability. These performance and scalability issues are many a time limited by the maximum limits imposed by the container size. Most virtualisation solutions continually work on this by bringing out solutions with bigger container sizes. The most recent example is VMware's latest ESX server version that has come with double the container size.
Performance overheads that the hypervisor brings in is another area that still needs work. "Stability of the hypervisor in terms of performance overheads is one of the main concerns in server virtualisation. The challenge is to bring it down to 1.5 or 2 percent from the usual overheads of 8 to 10 percent," states Arnab Roy, National Sales Manager, Datacentre Practice, Sun Microsystems India.
Security issues come next. While vendors cry themselves hoarse about the security that server virtualisation brings in, the fact remains that virtualised environments are as insecure as normal set-ups. What's more, these may be even more insecure at times due to API glitches and the like. This means that all the security measures taken for a normal server environment have to be applied to the virtualised environment as well. Special measures, such as training staff to deal with the new set-up's intricacies, will also have to be undertaken.

Hypervisor flavours

Hypervisor approaches also differ in terms of the way the interfacing of VMs with the hardware happens. Two of the common approaches used on this front are full virtualisation and paravirtualisation.

Proponents of full virtualisation include VMware, which depends on this approach for most of its solutions. Paravirtualisation is endorsed by vendors such as Xensource for their Xen solutions.

The difference between the two approaches lies in paravirtualisation’s use of APIs between the hypervisor, virtual OSs and hosted applications. (Figure 1: Full virtualisation vs paravirtualisation, highlights the differences between the two approaches.)

Many of the OS and CPU options available today are not optimised for virtualisation. Paravirtualisation attempts to rectify this shortcoming by using procedure calls for CPU instructions that are difficult to virtualise. This helps paravirtualisation tweak the virtual OS by modifying it to achieve better hardware performance.

On to the hardware front

Mukund Ramaratnam

Marketing & Business Development
AMD India

While software virtualisation can work wonders, maximum efficiency can be achieved only if the hardware is in sync with the software. This is one area where AMD and Intel step in with their CPU virtualisation processor technologies.

AMD’s Virtualization Technology (nee Pacifica) and Intel’s Virtualization Technology attempt to bridge the software-hardware divide by making virtualisation-aware CPUs. Intel has added virtualisation support for its latest dual core Itanium (Montecito) as well, which expected to be launched in mid-July (at the time of writing).

Both the CPU majors are clear that their attempt is not to replace third-party virtualisation software. “Virtualisation technology for the processor is not going to do away with the hypervisor. Instead, the role of virtualisation-enabled CPUs will be to accelerate the entire process,” explains Mukund Ramaratnam, Director, Marketing & Business Development, AMD India.

Narendra Bhandari

Regional Manager, APAC
Strategic Relations
& Internet Solutions Group
Intel Asia Electronics

“The objective is to optimise the entire CPU platform for virtualisation with support from a hardware and virtual machine perspective. Third party VM monitors are able to understand the hardware better and optimally use it. This is done using methods such as better instructions and efficient I/O for hardware-assisted virtualisation platforms,” says Narendra Bhandari, Regional Manager, APAC, Strategic Relations & Internet Solutions Group, Intel Asia Electronics.

Both vendors have started bringing out CPUs that are virtualisation optimised. As the movement gathers force, server virtualisation is also getting many of its kinks ironed out.

The bigger virtuality

The virtual I/O concept aims to create virtual server, storage and networking clouds for easier consolidation, re-allocation and management of server-server, LAN/WAN
and storage resources

Virtualisation has made inroads into many aspects of the infrastructure such as storage and networking as well, so the question which arises is how server virtualisation fits in.

This deserves a closer look at the virtual I/O concept. This concept aims to create virtual server, storage and networking clouds for easier consolidation, re-allocation and management of server-server, LAN/WAN and storage resources. There are several approaches in vogue today to create this, using consolidated channels like InfiniBand.

However, irrespective of the hardware or software used, three basic capabilities will be required for a proper virtual I/O setup. These are the capabilities to create virtual servers, virtual networking, and virtual SCSI. Virtual networking is made possible using virtual LAN, whereas virtual SCSI can be achieved using storage virtualisation technology.

At this point of time, virtualisation manager software (like the IBM virtual I/O server) is available to orchestrate the functioning of such environments. However, virtual I/O is still at its initial stages, and has a long way to go before it can really make a difference to the virtualised world. Till then it is better to go one virtualisation step at a time. You could consider starting with the server virtualisation step.