Expanding remote and mobile workforces are bringing a gigantic wave of personal devices into the workplace. As the demand for a bring-your-own-device (BYOD) policy intensifies, many IT organizations are considering virtual desktop infrastructure (VDI) deployment. VDI allows organizations to nimbly and cost-effectively support a mobile workforce while extending the efficiency of server virtualization to the desktop environment.

However, cost and management associated with storage for VDI deployments can be a significant challenge. VDI storage requires the capacity to store not only desktop virtual machines, but also the associated end-user application data. Storage for VDI should also deliver the performance necessary for handling utilization spikes of short duration—I/O storms—such as those generated when large numbers of virtual desktops are booted simultaneously or hundreds of end users log in or log off at the same time.

Dell EqualLogic PS Series iSCSI hybrid arrays are designed to minimize the cost and complexity of storage and are well suited for VDI environments. These hybrid arrays combine both solid-state drives (SSDs) and traditional hard disk drives (HDDs) in the same chassis and include features such as automated data tiering and centralized management tools to support efficient VDI deployments.

Combining SSDs and HDDs in a single Dell EqualLogic PS Series hybrid array enclosure helps optimize performance, capacity, and scalability for the multi-tiered workloads that characterize VDI deployments. Intelligent EqualLogic PS Series software with automated tiering capabilities places the frequently accessed base desktop virtual machine image on low-latency, high-performance SSD storage to help ensure maximum performance. Less frequently accessed data such as end-user application files are placed on low-cost, capacity-optimized HDDs, enabling organizations to meet VDI performance demands without costly over-provisioning.

Dell performs rigorous testing to create reference architectures for VDI platforms to provide organizations with guidelines regarding sizing and best practices for VDI deployments. To that effect, we have recently published a technical white paper providing storage sizing guidance and best practices for designing and deploying VMware View 5.1 based VDI environments using the EqualLogic PS6100XS array.

The paper demonstrates how an 830 task worker virtual desktop environment can be deployed in the chosen VDI infrastructure while leveraging a single PS6100XS array. Details are provided for the storage I/O characteristics under various VDI workload scenarios like boot and login storms along with performance characteristics throughout the VDI stack (ESXi server performance and user experience as determined by Liquidware Labs Stratusphere UX). 

In the test environment, the PS6100XS array delivered approximately 14,500 IOPS during a boot storm with a read/write ratio of about 76% / 24%. More detailed capacity and sizing guidelines can be found in the paper.


Figure 1: PS6100XS performance during boot storm due to simultaneous restart of 830 desktops

One final note: In View 5.1, VMware introduced View Storage Accelerator, which optimizes storage load and improves performance by caching common disk blocks while reading virtual desktop images. View Storage Accelerator uses the VMware vSphere platform feature called Content based Read Cache (CBRC) implemented inside the ESXi hypervisor.

We conducted tests to determine the impact of View Storage Accelerator on an 800 desktop deployment with CBRC enabled and disabled. The tests indicated 68% read IOPS reduction for this environment, leading to a better desktop density in the EqualLogic hybrid array. The paper has a detailed analysis on the resulting reduced of cost per desktop.


Figure 2: CBRC effects on VDI workload

Check out the paper here for all the findings, guidelines and recommendations for VDI storage.