April 10, 2012, 7:38 AM — This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter's approach.
One of the most significant cost elements with VDI is the centralized storage required for maintaining virtual machines. Hypervisor vendors argue that to get disaster recovery and high availability the additional expense is really a bargain. And in many instances that might be true. But in many cases cost is paramount, complexity is to be avoided and three or four nines of availability may be far down the list of priorities.
Availability and uptime are always important, but don't forget that moving from traditional desktops to a VDI architecture will improve uptime and availability regardless of whether centralized storage is used. So the real question is whether a fairly significant improvement in availability is good enough if it comes with low-cost, reduced complexity and fewer moving parts. Many IT shops will probably nod in the affirmative.
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Centralized storage is typically implemented with storage area networks that provide redundancy, network accessibility and management features that go beyond conventional, local storage. For example, SAN management tools allow you to add disks to your array(s) without discontinuing service. And hypervisors leverage these capabilities to deliver improved uptime and high availability through support of features like live virtual machine migration (also referred to as VMotion in VMware parlance).
In the event that a hardware failure occurs on the server running your VM, you can use these live migration techniques to transfer a VM to a different server, thus maintaining continuity of service. These features don't, however, make you immune to application crashes, OS crashes or many of the inherent instabilities in the OS and platform stack that don't have anything to do with hardware.