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VDI storage: Capacity and performance requirements for VDI implementation

Find out how to properly implement VDI storage in your environment in this FAQ. Learn about capacity and performance requirements, problems that arise, and how to fix them.

VDI storage can present several challenges to data storage administrators. Storage for virtual desktop infrastructure (VDI) can’t simply just be installed in your environment; you need to do some planning, including determining exactly how much storage you need for your VDI environment, deciding what your performance and capacity requirements will be, and what to do when problems arise.

In this FAQ, Ruben Spruijt, senior technical consultant for Netherlands-based PQR, discusses VDI storage requirements. Find out how to design your VDI solution, the impact VDI has on storage and how to solve capacity and performance problems in a VDI environment.

Read the transcript below or listen to the podcast on storage for a VDI environment.

How do you determine how much storage you'll need to support a new VDI installation?

VDI storage is deep impact, and … I think it's key to understand the theory about VDI and storage. How do you determine how much storage you'll need to support a new VDI installation? It's key to investigate the purpose of VDI, so that's the first starting point. Assess your current application usage and user profiles. It's key to design the VDI solution in a proper way. So part of this design is a discussion about stateless and stateful virtual machines (VMs). Stateless, also known as full VMs, and stateful, also known as assigned VMs. Stateless and stateful … have a big impact in sizing the VDI and storage solution. Also, [another] key component is the role of application virtualization in VDI. Ask yourself, is application virtualization being used in a solution? Or, what is the usage of application virtualization? [For example, is it] shared cache? These are also components in determining the impact of storage and VDI. Also, the role of client management solutions … form a role in storage requirements. And storage requirements are two-fold: Storage requirements from a gigabyte or terabyte perspective, and requirements from an IOPS perspective. All of these requirements -- stateless, stateful, the role of application virtualization, the role of client management solutions, and also the usage of applications and the usage of the different users -- form the basis of designing the VDI scenario [as well as] the storage scenario for a VDI implementation.

How do you make decisions around what the performance and capacity requirements will be?

[The] key is the design, or the best practices while designing, and there are a lot of handbooks, best practices, reference architectures for VDI and storage. But there are two key elements in this decision. The first one is [to] make sure that the VM for VDI is polished so that the VM doesn't generate the amount of IOPS as you normally do when you're just installing the operating system on a clean machine. So a best practice is to polish the VM so that the amount of IOPS this VM consumes is as low as possible. For instance, within a project VRC (Virtual Reality Check), we investigated all the best practices in the VDI space for Windows XP and Windows 7 to polish [and] optimize the VM. So that's the first step. You want to make sure you consume as [few] IOPS as possible.

The second step is understanding the theory about the impact of VDI in a storage space. The impact of VDI in a storage space [has] three steps: The impact has to do with the write penalty on the storage platform; the impact has to do with the read/write ratio of applications and OS; and the impact has to do with the latency included in this storage platform. These three are key to understand before you really design the storage solution. … When you understand the theory, then you can find the solutions to solve this VDI in storage deep-impact discussion. In essence, there are a lot of [vendors that offer solutions] in the storage space. The obvious ones there are the big vendors: 3PAR, EMC, [Hewlett-Packard], NetApp and a bunch of other vendors in this space. There are also smaller vendors, like Fusion-io. … There are a lot of vendors in this space who can help you with solving in some way the VDI storage discussion. … Understanding the theory and then determining how to solve this issue is the [main] approach here.

Once the VDI environment is up and running, if capacity or performance problems come up because they were undersized, how difficult are those problems to fix? Are capacity problems easier to solve than performance problems?

The question is two-fold. … The capacity problems are easier to solve because that is just adding disks or adding spindles. And also, performance problems are easier to solve because in the traditional storage space, just adding spindles or disks will solve in some degree these performance issues. But that will cost a lot of money. So the main question in that area is: Is it worth the money, and do you have the money for it? … But for a lot of customers it is not so easy to determine the performance problems from a storage perspective. For VDI there are [a lot] of moving parts … and determining the performance issues on the storage level is part of this, but it's not that easy. So the storage administrators must not only focus on the amount of free … gigabytes or terabytes [they have], but also must determine and monitor the range of IOPS which are still available for this storage platform.

For capacity management, not only from a capacity (gigabytes or terabytes) perspective, but also from an I/O perspective, is key for VDI. When this is not in place in your current solution, then it is [important] to add capacity management from a storage perspective while adding VDI to this environment.

A good approach can be, as well, to size a different storage platform for VDI. I know several customers who are in this space as well. It is not obvious or common to use your current storage platform … for thousands of VMs or VDI without re-evaluating the current storage platform. So re-evaluating the current storage platform will determine how much capacity you need from an IO and gigabytes perspective before you really land the VMs in this platform. [In other words,] you must design, understand the theory and discuss the solutions in the market space around VDI and storage. I mentioned just a handful of vendors, but there are a bunch of vendors in this space who can solve this VDI and storage deep-impact discussion.

This was last published in April 2011

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