Managing storage for virtual desktops


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Other helpful storage features

Storage arrays come bundled with many features that can help offload methods and processes that might normally be done elsewhere. Allowing the storage array to handle the things it does best can increase efficiency and performance. Here are some storage array features that can be beneficial in a VDI environment.

Data protection. Features, like Microsoft Volume Shadow Copy Service (VSS), that save previous versions of changed files, can make it easier for users to restore their own files. But implementing this feature on all user desktops can cause undesirable overhead and increase storage array I/O. With FalconStor's NSS SAN Accelerator, you can load an agent into the VDI gold master desktop template that allows the virtual desktop to communicate with the NSS SAN Accelerator appliance so any file changes that occur inside the guest OS are backed up by the appliance. Files can be recovered by users who can browse through previous versions and restore files to their desktop without involving the back-end storage device.

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Avoiding I/O spikes

Events that cause I/O spikes like boot storms can't be avoided, but other operations that cause I/O spikes can be. Use staggered schedules when performing antivirus scans/updates, as well as patching and updating operating systems and applications. By spreading the load across a longer period of time, you can avoid concentrated I/O on your storage system. And you can offload antivirus processing from the guest OS layer and move it to the virtualization layer where it can run more efficiently. VMware Inc.'s vShield Endpoint can offload antivirus scanning to a dedicated virtual appliance eliminating the need to run A/V software inside the guest OS. This greatly reduces the number of instances of antivirus you have to run on your hosts and, because it's centralized, it's easier to manage and the resource usage is greatly reduced.



Data deduplication. Data deduplication can greatly reduce the amount of storage you'll need for your virtual desktops, especially if you're using full image virtual machines (VMs) instead of linked clones. If you have 100 desktops, each with a 20 GB disk, you'd need approximately 2 TB of desktop space. But VDI users typically run the same OS and use many of the same applications, so there's lots of duplicate data. Data deduplication can reduce the amount of disk space needed when using full image virtual desktops by as much as 90% and reduce the 2 TB to 200 GB. With linked clones, a single master disk is shared with all writes saved to a delta file, which may be only 2 GB to 5 GB. But if you plan to use full images, data deduplication is a must.

Thin provisioning. Linked clones are already space efficient, so thin provisioning won't provide much of a benefit. But when using full image virtual desktops, thin provisioning can be a huge space saver, allowing you to overallocate storage. Thin provisioning coupled with data dedupe can provide tremendous space savings when using full images. Thin provisioning can be done at the storage array layer or virtualization layer. While you can implement it at both layers in a dense VDI environment, it might make more sense to offload it to the storage array so there's less overhead on the virtualization layer. It also simplifies management by only having to monitor and manage thin disks in just one area.

VMware vStorage APIs for Array Integration.VMware Inc.'s vStorage APIs for Array Integration (VAAI) allow storage-related tasks normally performed by the virtualization layer to be offloaded to the storage system, including data copy operations (cloning, Storage vMotion), disk block zeroing and vmdk file locking. Leveraging VAAI in a VDI environment can provide benefits, as disk operations can be completed quicker and more efficiently than can normally be done by the hypervisor. VAAI is still rather new, and adoption and integration by storage vendors is still a work in progress, but storage arrays that support VAAI can provide some good benefits today and probably even more as the technology matures.

Know your needs

There are many things to consider when designing storage to support a virtual desktop infrastructure environment. While budgets may limit some of your options, there are a number of creative solutions available that can help you get the performance your virtual desktops will require. But the first step is to know your requirements; a proper assessment will help you define storage requirements that will, in turn, help you implement a properly sized storage solution. With a right-sized storage system in place, you can enjoy the benefits of VDI without worrying that your storage system will become a bottleneck for your users.

BIO: Eric Siebert is an IT industry veteran with more than 25 years of experience who now focuses on server administration and virtualization. He's the author of VMware VI3 Implementation and Administration (Prentice Hall, 2009) and Maximum vSphere (Prentice Hall, 2010).


This was first published in March 2011

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