Desktop Virtualization – The Right Way (Part 2)
One of the questions an architect must ask themselves when designing a desktop virtualization solution (VDI) is understanding user patterns. User patters have a direct impact on a virtual desktop design and also on the overall scalability of the solution. A user lifecycle consists of four phases:
- Boot
- Logon
- Work
- Logoff
Two common work scenarios can impact a virtual desktop environment:
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Scenario 1: 9-5: In this scenario, all users logon in the morning and logoff in the evening. There might be some sporadic users working after hours, but for the most part users stay within these working hours.
To design this environment, the architect needs to make sure that the boot up storm doesn’t overwhelm the environment. If the environment includes a large number of hosted virtual desktops, it has a direct impact on your hypervisor of choice, the storage infrastructure and the network infrastructure. An architect can easily overcome any challenges with a boot up storm in this scenario by staggering the virtual desktop bootup sequence before users arrive to logon. The pre-booting process allows the system to calm down before the logon storm hits.If one has 1,000 desktops (across 10-20 servers) that must be ready by 9 AM, and you assume each desktop takes 30-60 second to fully boot, you want to start your bootup sequence by at least 8:30.
The second aspect is the logon storm. There is little that can be done to the environment to spread the storm over a greater amount of time as it is based solely on the users. The logon storm is going to have a direct impact on the infrastructure and any solution must be design appropriately.
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Scenario 2: 24/7 (3 shifts): This scenario brings about a few more challenges in that users are always online. The organization is running 100% of the time and as users are connecting, other users are logging off. The cycle continues over and over again. This architecture is really dependent on the environment in question. Even though the organization might be 24/7, those shifts might be located around the world in different locations connecting to different data centers (follow-the-sun model). But if we have a unique scenario where we have 1 data center and all shifts connecting to that 1 site, this type of an environment would make us change our design as follows (safe to assume that all shifts are different sizes. In fact, many 24/7 models located in one site have one large shift and the remaining 2 shifts are significantly smaller).
In the 24/7 scenario, we need to allocate enough resources to go above our maximum levels of concurrency per shift. This allows extra breathing room during a shift change where we have active users, users logging on, and users logging off. We also need to prevent the bootup phase from occurring during our largest shift changes as the bootup process has the greatest impact to the underlying infrastructure.
Two different user pattern scenarios to think about during a desktop virtualization design.
Daniel Feller, Lead Architect of Worldwide Consulting Solutions for Citrix, is responsible for providing enterprise-level architectures and recommendations for those interested in desktop virtualization and VDI. He is charged with helping organizations architect the next-generation desktop, including desktop virtualization, VDI, client hypervisors, and application virtualization.
In his role, Daniel has provided insights and recommendations to many of the world’s largest organizations across the world.
In addition to private, customer-related work, Daniel’s public initiatives includes the creation of best practices, design recommendations, reference architectures and training initiatives focused on the core desktop virtualization concepts. Being the person behind the scenes, you can reach/follow Daniel via Twitter @djfeller.
Tags: Desktop, Virtualization