VDI Storage Should Do More than Just VDI

What do companies expect from a VDI project? In the long run they expect more flexible device deployment, lower desktop support costs, and better protection from device and data loss. But short term, a VDI deployment can’t make things worse for the user. Their virtual desktop needs to perform as well or better than the physical desktop that is being replaced. That means that the VDI infrastructure (specifically the storage system) needs to provide consistent predictable performance, flexibility, scalability, and reliability.

But what if the storage brought in for VDI could benefit other applications as well? Many VDI projects drive the purchase of new storage systems to handle the unique performance demands of VDI. But if storage systems exist that can do more than just VDI – like being able to support other application servers – maybe companies should expect more from their VDI storage solutions.

What IT Needs from VDI Storage

To deliver the same or better user experience, the storage system must maintain that performance through all the ups and downs in I/O demand during the workday that are common with VDI. This includes the morning boot or login storm as well as the very write-intensive I/O profile that’s common throughout the day. Meeting this demand requires a storage system that can integrate memory-based storage, like flash, and intelligently apply that technology in the most efficient, predictable, cost-effective way possible.

Click to Watch The On Demand Webinar "The Waste of a VDI-only Storage Solution"

Hybrid or All-Flash

All-flash arrays are the simple solution when consistent performance is a requirement. After all, putting all the data on flash can guarantee performance in any workload scenario, up to the capacity of the array. Also, that performance is very consistent, since there is no risk of a high latency read coming from hard disk. But the cost of most all-flash systems may be out of reach for many organizations, especially as capacities grow.

Hybrid systems, with both disk and flash capacity, are a good alternative but users must be able to differentiate between the hybrid architectures available in order to make the right choice. Clearly hybrid systems win on cost effectiveness, but how can they deliver the steady, predictable performance that’s essential for VDI? After all, if the data needed is not stored in flash or if new data needs to be written to the hard disk, tiered storage consistency is put at risk. And the resulting inconsistency can lead to user dissatisfaction and eventually the abandonment of the project.

Quality of Service

Assuring certain workloads will maintain consistent performance is the key to delivering a VDI storage infrastructure that meets user expectations. True Quality of Service (QoS) means being able to guarantee performance levels by application business priorities. Administrators don’t have the time to manually manage flash and hard drive tiers for each specific application running on them. They instead need a system that will allow the IOPS, throughput and latency performance to be hard-set to specific workloads or volumes. This workload-driven QoS provides a ‘set it and forget it’ capability that busy IT professionals need.

Write First to Flash

After the morning boot or login storm, most VDI workloads are write-heavy throughout the business day until the evening logout or virus scan. When a lot of write activity occurs, disk drives can get overwhelmed, increasing latency and creating unpredictable performance for users. A key weakness of most hybrid systems is that they leverage flash in a “write-through”methodology. This means that while data is captured in the flash tier for subsequent reads, the user or application is still at the mercy of disk latency for any new or modified data. Given the reliability of flash and the high availability in most hybrid storage systems, this should no longer be needed. A well designed hybrid system should take a ‘flash first’ approach, where all writes are written to flash and later sent to the hard disk tier without risking data safety.

Server-side Flash

Another common work-around for VDI storage performance problems is putting flash in the server and using it for read caching. These techniques can improve VDI performance and pull some of the demand off of the shared storage system. However, if the server-side flash isn’t integrated with the shared storage they can conflict with each other. This means potentially “double caching”active data, which wastes expensive flash capacity and increases latency as two cache algorithms have to process data before a result can be returned. A hybrid array that’s integrated with server-side flash can boost storage I/O performance and boost the efficiency and effective capacity of both storage resources.

Scalability, Flexibility, Efficiency

Of course, the system needs enough flash capacity to support the spiking IOPS workloads that characterize the VDI environment and whatever other applications are loaded onto it. Obviously, this requires the horsepower to do both jobs – VDI and other applications – even at peak VDI periods. Hybrid arrays that use PCIe instead of drive form-factor SSDs, better utilizes flash performance and allows flash to be added without consuming disk drive slots. And, enabling the expansion of drive shelves maximizes the system’s total capacity. In this way performance can be scaled independently from overall storage capacity, without involving disruptive controller upgrades, giving the system the flexibility to support essentially any workloads in the data center.

Getting more than VDI from VDI Storage

Selecting a hybrid storage system with these characteristics certainly helps it support the demanding VDI use case. But armed with these capabilities, the VDI storage system can certainly do more. If the storage system can provide an integrated QoS capability along with the right combination of performance, capacity and price, the same hybrid system can be used for other environments as well, like virtual servers or bare metal databases.

A VDI solution that could support other environments within the data center would be a coup for IT, especially in small-to-medium sized enterprises where system admins and budgets are already stretched thin. If the storage was justified by the VDI project, the other environments could benefit from a performance boost — essentially for free — or at least making the ROI on the storage system much easier to achieve. Having a hybrid storage system that can handle the demand, again, while maintaining consistent performance via QoS for all users and environments, could give IT more than it expected from a VDI project.

What the Right VDI Storage can Bring

By raising their expectations of their VDI storage infrastructure an IT organization can easily end up with a system that addresses their wider shared storage needs as well. With an array like ioControl Hybrid Storage from Fusion-io, they can get the performance of PCIe flash, better capacity with a hybrid array and more storage consolidation with flexible flash and disk expansion. Plus they have the option of the additional performance boost of integrated Fusion-io server-side flash and read caching. All of these benefits are made possible by an intelligent QoS functionality that uses a policy-based performance management mechanism and allows admins to prioritize workloads based on business importance.

Click To Watch On Demand

Click To Watch On Demand

Fusion-io is a client of Storage Switzerland


Eric is an Analyst with Storage Switzerland and has over 25 years experience in high-technology industries. He’s held technical, management and marketing positions in the computer storage, instrumentation, digital imaging and test equipment fields. He has spent the past 15 years in the data storage field, with storage hardware manufacturers and as a national storage integrator, designing and implementing open systems storage solutions for companies in the Western United States.  Eric earned degrees in electrical/computer engineering from the University of Colorado and marketing from California State University, Humboldt.  He and his wife live in Colorado and have twins in college.

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