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How a virtualization stack provides simplicity, scalability for VDI

VDI products can run on integrated virtualization platforms, bringing simplicity and deliverability to VDI deployments. But converged infrastructure may not be suitable for all.

converged infrastructure is all the rage in server virtualization, but when it comes to VDI, these pre-bundled, integrated platforms won't suit every organization.

I call these converged infrastructure appliances "stacks" because they offer pre-packaged IT hardware and virtualization platforms. For virtual desktop infrastructure (VDI) customers, a virtualization stack allows them to size their chosen platform to fit their desktop needs and grow as needed. However, integrated virtualization platforms aren’t the best choice for small VDI environments, and they don’t lend themselves to customization.

The first of these integrated virtualization platforms reached the public when VMware Inc., Cisco Systems Inc. and EMC Corp. produced Vblock. NetApp Inc., VMware and Cisco now offer the FlexPod, which allows customers to customize the virtualization stack a bit more than Vblock. Hewlett-Packard produces the Matrix product, now called Virtual System -- the only single-vendor converged infrastructure offering in the game.

Why go for converged infrastructure?

For customers, the attraction of integrated virtualization platforms is the simplicity: Buy the right-sized virtualization stack and just load on your virtual machines (VMs). Someone else did all the work to get the firmware and drivers right, which eliminates the potential nightmare it can be in a complex environment. Plus, having everything factory-integrated is pretty cool, with all the rack layouts and cabling both optimized and very pretty.

The attraction of converged infrastructure for vendors is the deliverability of a single-order item. The vendor can do the integration of different parts once on a collection of components it controls. Integrated virtualization platforms get rolled out in cookie-cutter fashion, so every customer gets the same basic configuration and it always works the same. Plus, support cost is much lower because customers are running pre-tested configurations.

So, if a pre-bundled virtualization stack is a good way to run VMs, is it a good way to run virtual desktop infrastructure (VDI)?

Benefits of VDI products on virtualization stack

Pre-bundled, integrated virtualization platforms allow VDI customers to right-size their model based on the number of desktops they use and lend to future growth.

Infrastructure size: Customers usually select a virtualization stack based on how many VMs each model will support. They generally buy a slightly bigger size than they feel they will need. If they need 800 desktops, they buy 1,200; and if they need 3,000 desktops, they may have to buy converged infrastructure with a nominal capacity of 4,000. The actual number of desktops the platform can accommodate also depends on the desktops' workload. (For instance, 800 Oracle Forms users are very different from 800 Microsoft Word users.)

The converged infrastructure load will also be different for different VDI products. VMware View generally requires shared storage and often places a huge load on it, so the storage composition is critical. Citrix XenDesktop can operate with mostly local storage and stream across the VM network, placing a greater load on networking.

Scalability: The starting point for VDI stack size seems to be about 1,200 users in a single rack, and organizations can then size multiple racks based on larger user counts. This count could put a 10,000-user desktop deployment in a single data center row. The modular scalability of converged infrastructure can be a huge benefit for organizations with unpredictable growth. A pre-bundled virtualization stack provides the basic building block and organizations can scale their VDI products by repeating the pattern.

More on converged infrastructure:

Death to white box servers: Why converged infrastructure is superior

Boosting data center efficiency with converged infrastructure hardware

Navigating the converged infrastructure hype cycle

Support: Running VDI on integrated virtualization platforms also allows customers to place much of the desktop support inside the stack. User profiles and home directories stored inside the virtualization stack minimize the network load outside the rack. (As an extra benefit, this setup also allows easier scaling, but causes slightly lower VDI density per rack.)

Converged infrastructure vendors have been good about supporting many different VDI products on their virtualization stacks. There are useful reference architectures for VMware View and XenDesktop on HP's Virtual System and Vblock. (Interestingly, both references usually show the same user density for both VDI products.)

When VDI won't work with converged infrastructure

Despite the benefits of converged infrastructure, deploying VDI on a pre-bundled virtualization stack isn't always the best idea. Some customers have a VDI environment that's too small for even the smallest stack. If you only have 500 staff members and even fewer virtual desktop users, for instance, the smallest virtualization stack will probably still be too large, resulting in the waste of money and resources.

Running VDI products on converged infrastructure also won't work if you want to tweak and tune components to minimize cost. These integrated virtualization platforms come pre-tuned by the vendor, and you can't usually pick your own components. The IT department has to simply use it as is to run workloads.

Converged infrastructure offerings can provide a great platform for large VDI deployments that need to scale significantly. Deploying VDI products on a pre-bundled virtualization stack also allows organizations to concentrate more on the all-important end user experience.

Alastair Cooke
is a freelance trainer, consultant and blogger specializing in server and desktop virtualization. Known in Australia and New Zealand for the APAC virtualization podcast and regional community events, Cooke was awarded VMware’s vExpert status for his 2010 efforts. Follow him on Twitter @DemitasseNZ.

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