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March 21, 2012

Overcoming the VDI IOPS Challenge – VMware View 5 Reference Architecture

Seth Knox - Atlantis


Correct IO sizing is always a big challenge for customers adopting VDI. Storage can represent more than 60-70% of the total desktop cost in VDI infrastructure. Get it right and the project is successful – users accept it and desktop cost is low. Get it wrong and the desktop is very expensive and the team does not get to scale beyond the first implementation – or the desktop is inexpensive and users reject it for performance reasons.  This challenge becomes amplified when IT tries to use VDI as a means to simplify migration from Windows XP to Windows 7.

Here’s why….

The Windows OS was designed with a local and dedicated disk and requires constant access to the hard drive even when it is idle. In addition, the Windows OS will consume as much disk IO or throughput to the hard drive as is available. Windows desktop workloads are write heavy (70-80% writes, 20-30% reads) .Windows 7 OS images are also larger than XP images, forcing enterprises to buy more storage capacity to accommodate larger numbers of users.( a Windows 7 image ranges from 25GB to 50GB or more depending on the components and apps installed)

There is another problem with IOPS when it comes to VDI. All IOPS coming out of virtual desktops are typically treated as “equal” by the hypervisor. This causes a lack of consistent user experience (as user workloads vary). Imagine a user running a zip file compression or running an on-demand virus scan on the same host as the CEO who needs his desktop to work on his board meeting presentation. This can be a recipe for disaster.

So why is IOPS a limiting factor?

Essentially the problem comes down to the physics of a spinning disk. In a traditional hard disk drive there is a spinning platter which is why all disks have an RPM value. Each disk can provide 65-200 IOPS per spindle depending on what type of disk is being used (SATA, SAS).  Customers sometimes size for the storage capacity or average IOPS. Both these approaches may result in under sizing the storage.

The Limitations of SSDs…

Solid state disks (SSD) are a popular solution when it comes to VDI. However, SSD based VDI forces customers to rely on stateless desktops. Unfortunately, enterprises are not always ready to re-engineer their images and integrate third party profile solutions so they can take advantage of stateless desktops. In fact, most customers prefer to start with persistent / stateful desktops and then migrate to stateless over time.

ILIO IOPS reduction

Looking for a Better Way?

There is another approach customers can take to overcome IO challenges which looks at optimizing storage. Atlantis ILIO is a NTFS aware storage optimization solution. With advanced IO processing and inline de-duplication ILIO offloads 80-90% of the read/write IOPS before it reaches the storage. This results in reduced storage capacity required (up to 90% lower) and provides high performance desktop due to the high write and read IO offload provided by ILIO. As it is a software based solution, Atlantis ILIO is storage and hardware agnostic –and  customers no longer need to worry about qualifying new hardware vendors or buying /adding new storage. ILIO is also optimized for both XP and Win7 images and supports stateless and persistent desktops.  And it works in conjunction with advanced vSphere features like vMotion / DRS / HA and FT.

So what does performance look like with ILIO? Well you can expect to support high performance desktops (300+ IOPS per desktop) with up to 90% less cost when it comes to storage. You can actually support 4 to 7x more users on your existing infrastructure – SAN, NAS, local disk or even diskless (memory) options.

Find out more about the IO offload and capacity improvements for a high performance desktop (300 IOPS – 2x you the PC performance) VMware View 5 desktop in the reference architecture published here.  This RA includes View 5, VMware ThinApp, View Persona and View Planner tools.

Useful Links

VMware View, Atlantis ILIO & Trend Micro Reference Architecture

Offloading Virtual Desktop IOs with Atlantis ILIO: Deep Dive  – By Andre Leibovici

View Calculator with Atlantis ILIO – By Andre Leibovici

Diskless VDI with Cisco UCS and Atlantis ILIO

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