VDI IOPS: Accelerating performance at a cost

When implementing VDI , a key consideration is how many IOPS should be allotted per desktop. However, providing desktops with enough IOPS so that the performance isn't compromised can be costly. In this video, VDI expert Brian Madden explains VDI IOPS requirements and argues the VDI performance shouldn't be sacrificed for a lower cost. Watch the video on VDI IOPS or read the transcript below.

For desktop virtualization for VDI, performance is way more important than capacity. … In enterprise storage this [may be] a general trend, but we absolutely have this in the desktop world. If you think about it … for server virtualization how many VMs are you putting on one host? Four? Six? Eight? Twelve? Twenty? Some smallish single-digit, two-digit number? With desktop virtualization, we're putting like, 200, 300 [VMs] per host. That's a lot of copies of Windows. Every one of those copies of Windows is having its kernel, and its driver, and its copies of Word, and its cache, and all that kind of stuff [copied]. And it's interesting … if you do the math -- let's look at IOPS. Even a 5400 rpm drive (like the slowest desktop drive) is 50 to 80 IOPS. This is our magnetic, spinning, regular, old-fashioned, 10-year-old desktop hard drive.

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So now we want to do some VDI, and put all these users on our servers, so let's start doing some math. So we break out our napkin, [we say] "Okay, I've got 50 IOPS per desktop." I'm going with the oldest slowest number, the slowest number on that chart, which is 50. Fifty IOPS per desktop, 200 desktops per host, so that's 10,000 IOPS per host. I've got six hosts (I'm making these numbers up), and I need 60,000 IOPS. So, I just call up my vendor to find what the cost is, and [it is far too expensive]. … So go back to the drawing board. I look at VMware and say "Fifty IOPS per desktop? You don't need 50, you need seven IOPS per desktop." We've got economies that scale -- 7 IOPS per desktop means I only need 1400 IOPS per host, which means I need 8400 IOPS total. How much does it cost me to buy 8400 IOPS? Hey, I can afford that. … Because if seven IOPS per user works, then why are we all putting SSDs on our laptops? And it's funny because we've got this pressure, you know? We've got this guy who sold us VDI, and one of the things he said was "VDI, it saves you money." So you can't go back to your management who bought off on VDI on the premise they're saving money and tell them you need 600 bucks per user just for storage. That doesn't work out for saving money. …

By the way, the way you fix [the cost problem] is not by hacking down your IOPS. The way you fix that is you don't try to save money with VDI.

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