Evaluating VDI storage options
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Until recently, if you wanted to take advantage of advanced VMware vSphere features such as vMotion or VMware High Availability, you'd have to invest in an expensive shared storage tool. For a lot of large companies, this isn't a huge deal because they probably already have a solution in place and the expertise to deal with it.
For small- and medium-sized businesses, though, storage has been a challenge. Adding big, complex storage solutions is usually outside the expertise of a small IT department -- let alone the company's budget. VMware's vSphere Storage Appliance (VSA) is an SMB-oriented solution that allows smaller vSphere implementations to use local disk while still taking advantage of some of vSphere's more advanced features.
The vSphere Storage Appliance works by creating a pool of storage locally on a host and mirroring that storage between the other hosts on a network. This approach, while not as efficient as shared storage, has the same effect by keeping the data synchronized. That means admins can now take advantage of vMotion, VMware HA, Fault Tolerance and a few other high-end features.
What does VSA mean for VDI?
Even though all the literature seems to be referring to server virtualization, I'm a desktop guy, so, naturally, I start to wonder about the desktop virtualization implications of this appliance. Specifically, I'm curious to see if using the vSphere Storage Appliance with VMware View is a viable option for organizations with small virtual desktop deployments. It turns out there is one main limitation, although for small environments it shouldn't be a big problem: the vSphere Storage Appliance is limited to three nodes.
Assuming you can build a server that can support 1400 IOPS using local storage alone, you should be able to safely run at least 50 virtual machines. Configuration changes can greatly affect that, but if the above scenario is true, it's conceivable that a three-server implementation of vSphere with the VSA could support 100 VDI desktops (leaving one host for n+1 redundancy) with room to spare.
Using Storage vMotion, which allows you to live migrate desktops between storage systems (not just within the same pool like regular vMotion), you can upgrade to a shared storage solution later, which means that for growing SMBs or simple installations at larger companies, upgrading requires a minimal amount of work.
At this point, I'm thinking the vSphere Storage Appliance is at least worth trying. If it works, it will save a ton of money up front, while still giving you the ability to grow without re-architecting your entire environment. My gut tells me the biggest benefit will be for pilot deployments, though. Now you can build a full-featured environment without having to spend big money up front on shared storage.
ABOUT THE AUTHOR:
Gabe Knuth is an independent industry analyst and blogger, known throughout the world as "the other guy" at BrianMadden.com. He has been in the application delivery space for over 12 years and has seen the industry evolve from the one-trick pony of terminal services to the application and desktop virtualization of today. Gabe's focus tends to lean more toward practical, real-world technology in the industry, essentially boiling off the hype and reducing solutions to their usefulness in today's corporate environments.