The wrong storage array can suck the life out of a VDI deployment. Before you virtualize desktops, determine your VDI storage requirements and whether your array can handle the extra load -- otherwise,
Virtual desktop infrastructure (VDI) workloads have different storage requirements than physical server workloads. Physical servers generally have steady storage requirements with occasional peaks and lows. The workload is usually made up of a small number of machines -- often less than 10 servers for every 100 staff members. VDI workloads, on the other hand, can be very quiet one minute, and extremely demanding the next. Plus, VDI servers are made up of many small loads -- possibly as many as there are users.
Adding VDI to your environment could drain the storage performance of existing servers, create VDI storage bottlenecks and bring your VDI deployment to a standstill. VDI storage requirements are much more unpredictable, so you need a storage array that can support more resources and a greater number of workloads. You may need to purchase a dedicated array for VDI storage, but if your environment is small enough, there are other options.
VDI storage depends on deployment size
Small VDI: If your expected VDI workload is smaller than the workload on your physical servers, you could use the same storage for VDI that you have in your existing environment. This will work, for instance, if you only virtualize about 5% to 10% of desktops and your storage array has a good amount of spare capacity. Since the additional load is light, it won't adversely affect the existing server load. Still, you should re-assess whether you need additional VDI storage if you start to roll out more desktops.
Large VDI: A larger VDI deployment is more difficult to accommodate. If you're virtualizing more than half your desktops, the added VDI load could be too large for your old storage array.
More on VDI storage:
Solving the VDI storage problem
VDI storage tips and tools
Virtual desktop storage basics: Storage allocation for VDI
VDI's storage hunger: Dollars per gigabyte and IOPS load don't mix
But before you run and buy new storage for VDI, check out your existing array and see if it can support segregation of your physical server load and VDI load. If you can guarantee good storage performance for the physical servers even while the VDI load stresses the storage array, then the two loads can coexist on one array. To segregate the different loads, it's best to have a storage array that's virtualization-aware or provides multi-tenancy.
If you can't segregate the server and VDI storage loads on one array, you'll need a new storage array just for virtual desktops. To get the best VDI storage performance, you may even need to select a completely different model or vendor than you use for your existing storage system. You could also try a different transport protocol, for instance, moving to IP-based VDI storage rather than the traditional Fibre Channel. You should also check out more advanced storage features, such as tiering or modular scale-out approaches.
Having the right storage for VDI is critical to a successful rollout. For a small VDI deployment, the existing storage array may be adequate, but larger implementations may require isolated workloads or a dedicated array for VDI storage. Make sure that the system you have fits your VDI storage requirements and that the storage and virtualization teams' needs are met.
ABOUT THE AUTHOR:
Alastair Cooke is a freelance trainer, consultant and blogger specializing in server and desktop virtualization. Known in Australia and New Zealand for the APAC virtualization podcast and regional community events, Cooke was awarded VMware’s vExpert status for his 2010 efforts. Follow him on Twitter @DemitasseNZ.
This was first published in March 2012