VDI storage presents a slew of new challenges to data storage professionals. We spoke with Ray Lucchesi, president at Broomfield, Colo.-based Silverton Consulting, about how supporting hundreds or thousands of simultaneous boots and shut-down cycles can hammer your system; how well direct-attached, SAN and NAS storage systems work in a VDI environment; and why performance and capacity might not be the most important factors when choosing your virtual desktop infrastructure (VDI) storage solution.
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SearchStorage: What storage challenges does VDI pose?
Lucchesi: For most installations, a virtual desktop infrastructure requires a different style of storage than what people might be used to. When you start combining 50 or 100 virtual desktops into one server, those 50 or 100 desktops could potentially be booting up at the same point in time -- Monday morning at 8:00 -- could be cycling down at 5:00 Friday evening, could be firing up an antivirus scan all at the same time. Compound that with potentially thousands of virtual desktops that larger enterprises are trying to work into a VDI infrastructure today, and you have some serious challenges from a storage perspective.
SearchStorage: Does VDI storage pose more of a performance issue or a capacity issue?
Lucchesi: There are certainly performance considerations for a virtual desktop infrastructure and performance spikes occur during boot time, antivirus scans and backups for those virtual desktops.
But in my mind it's not performance, it's not as much capacity, it's more advanced features. When you're replicating 50, 100 or even 1,000 of these boot C: drives for all these virtual desktops you have to support, you would like to not have to save or store all 1,000 images of those boot drives. Probably 95% of that is exactly duplicated across all 1,000 images. So you want something with some sort of data dedupe, almost at the sub-block or sub-file level.
Also, because everybody fires up Monday morning or Tuesday morning at 8:00 or whatever the timeframe for your business is, you want to have something that provides some special performance enhancements or caching for those boot images. Deduplication can help to some extent to do that, but there are other characteristic storage capabilities that can help as well.
The other thing you have to consider is that with hundreds or thousands of virtual desktops, you probably don't want to put that on direct-attached storage. You want to try to consider something from an external SAN or external NAS perspective, something with higher reliability and availability because if the storage goes down, 1,000 users or more would be out. You could possibly get by with direct-attached storage, but if there's a problem and you take those 1,000 users down, they're not going to be pleased.
SearchStorage: What do storage administrators need to do to prepare for a VDI implementation?
Lucchesi: The storage administration is tasked with identifying proper levels of storage that individuals can use. The issue to some extent with VDI storage is that the proliferation of VMDKs or virtual disk volumes is pretty high. So if you have 1,000 virtual desktops, it's 1,000 virtual disks you have to create and maintain.
One thing that can make this easier for an admin is to use something like NFS or a NAS system instead of SAN storage. It's pretty easy to create 1,000 files a NAS product, but a thousand logical volumes on block storage is certainly a challenge. If I was an admin, I'd look at moving to NAS with some of these other advanced features we talked about earlier.
SearchStorage: What storage technologies are best suited for VDI?
Lucchesi: I think NAS storage systems are pretty evident as something that you probably want to go after with a VDI infrastructure implementation. It's just a lot easier to maintain; it's a lot easier to create 1,000 virtual disk files rather than trying to create 1,000 LUNs or something of that nature. I think given the fact that you're creating 1,000 boot volumes that are effectively 90% to 95% exactly the same information from one virtual desktop to another, you want something that can deduplicate those 1,000 boot volumes into something considerably less.
Besides data dedupe, you can also do that with something called copy-on-write snapshot. When you do a snapshot, you copy the data anytime there's an update to it. You only store the updates to the data and point to the rest.
And the other things I touched earlier on were high reliability and high availability. Direct-attached storage might be cheaper, but I think you'd be much more satisfied with a highly available, highly reliable system. And that begs for enterprise-class storage and enterprise-class NAS.
This was first published in October 2010