Virtual desktop infrastructure workloads look different than they do in a virtual server environment because the applications are run from the data center rather than physical devices. Therefore, storage admins should use different criteria to choose the storage that supports the desktops.
At a Storage Decisions seminar in New York, virtual desktop infrastructure (VDI) expert Brian Madden highlighted those differences and the resulting VDI storage requirements. "With desktops, we have a lot more writes," he said. It's common for virtual desktops to see a 50/50 balance of reads to writes, while a server would process far more reads -- approximately 90%, according to Madden. "And that profile changes depending on what the user is doing. When the virtual machine boots up, it's all reads. When a user logs on and their profiles and applications come down, it's all writes -- and throughout the day it tends to balance out."
Just as virtualizing servers randomizes data, VDI randomizes reads and writes, meaning it's important to select storage that can handle the unpredictable nature of VDI. "It's much more random as to reads and writes and what files [users] are going after, so it's not as easy to streamline as it is with servers," Madden said.
But perhaps the highest profile reason why understanding VDI storage requirements is so important is because of latency. Virtual desktops are interactive, so latency is much more apparent to end users than it is in virtual server environments, a point Madden emphasized in his presentation. "What if your Exchange server is slow? That means it's slow to write an email, but the user doesn't know," he said. "But if it's on a desktop that's slow, [the user] clicks 'Start' and if the menu doesn't pop up, they're calling you."
Storage administrators who know the difference between VDI storage requirements and virtual server storage requirements are less likely to make a purchase decision based on existing technologies. According to Madden, choosing a particular storage technology for VDI because of vendor loyalty can be an ineffective method.