This document addresses the challenges associated with end-user computing workloads in a virtualized environment and suggests design considerations for managing them. It focuses on performance, capacity, and operational considerations of the storage subsystem because storage is the foundation of any virtual desktop infrastructure (VDI) implementation. Where possible, it offers multiple solutions to common design choices faced by IT architects tasked with designing and implementing a VMware Horizon storage strategy.
Typical Storage Considerations
Over the years, many end-user computing environments were designed, engineered, and built without proper consideration for specific storage requirements. Some were built on existing shared storage platform offerings.
Others simply had their storage capacity increased without an examination of throughput and performance.
These oversights prevented some VDI projects from delivering on the promises of virtualization.
For success in design, operation, and scale, IT must be at least as diligent in the initial discovery and design phases as in deployment and testing. It is essential to have a strong methodology and a plan to adapt or prefine certain elements when technology changes. This document aims to provide guidance for the nuances of storage.
Operating systems are designed without consideration for virtualization technologies or their storage subsystems. This applies to all versions of the Windows operating system, both desktop and server, which are designed to interact with a locally connected magnetic disk resource.
The operating system expects at least one local hard disk to be dedicated to each single instance, giving the OS complete control from the device driver upward with respect to the reading, writing, caching, arrangement, and optimization of the file system components on the disk. When installing the operating system into a virtual machine running on a hypervisor, particularly when running several virtual machines simultaneously on that hypervisor, the IT architect needs to be aware of factors that affect how the operating system works.
VMware Horizon Architecture
Figure 1 presents a logical overview of a validated VMware Horizon® 6 design. The design includes VMware Horizon with View, VMware Workspace™ Portal, and VMware Mirage™, along with the recommended supporting infrastructure. These components work in concert to aggregate identity, access, virtual desktops, applications, and image management in a complete architecture.
Capacity and Sizing Considerations
The primary storage considerations in an end-user computing infrastructure have two dimensions: performance and capacity, which are the focus of this paper.
Importance of IOPS
Input/Output Operations per Second (IOPS) is the performance measurement used to benchmark computer storage devices devices such as hard disk drives (HDD), solid-state drives (SSD), and storage area networks (SAN). Each disk type discussed in this document has a different IOPS performance statistic and should be evaluated independently.
When you consolidate multiple virtual machines and other user workloads on a hypervisor, you should understand the typical storage performance expected by a single operating system. This requires an understanding of the added contention for access to the storage subsystem that accompanies every subsequent guest operating system that you host on that hypervisor. Although IOPS cannot account for all performance requirements of a storage system, this measure is widely considered the single most important statistic. All the virtual assessment tools offered by VMware partners capture granular IOPS data, giving any IT architect the ability to optimize the storage accurately for end-user-computing workloads.
The Impact of Latency
Latency can definitely affect performance and in some cases might actually have a greater impact than IOPS. Even if your storage can deliver a million IOPS, it does not guarantee your end users an enjoyable virtual desktop or workspace experience.
When assessing latency, always look up and down the storage stack to get a clear understanding of where latency can build up. It is always good to start at the top layer of the storage stack, where the application is running in the guest operating system, to find the total amount of latency that the application is seeing. Virtualdisk latency is one of the key metrics that influences good or bad user experience.
Download out the full VMware Horizon 6 Storage Considerations technical white paper.