DELL. Virtual Desktop Infrastructure Study END-TO-END COMPUTING. Dell Enterprise Solutions Engineering

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1 DELL Virtual Desktop Infrastructure Study END-TO-END COMPUTING Dell Enterprise Solutions Engineering 1

2 THIS WHITE PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES. THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND. Dell, the Dell logo, PowerEdge, PowerVault, and OptiPlex are trademarks of Dell Inc; AMD is a registered trademark and Opteron is a trademark of Advanced Micro Devices, Inc.; Intel, Celeron, and Xeon are registered trademarks and Core is a trademark of Intel Corporation in the U.S and other countries; Microsoft, Windows, Windows Vista, Microsoft Word, Active Directory, Excel, Internet Explorer, and PowerPoint are either trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries; VMware is a registered trademark of VMware Inc. Other trademarks and trade names may be used in this document to refer to either the entities claiming the marks and names or their products. Dell disclaims proprietary interest in the marks and names of others. Copyright 2008 Dell Inc. All rights reserved. Reproduction in any manner whatsoever without the express written permission of Dell Inc. is strictly forbidden. For more information, contact Dell. Information in this document is subject to change without notice. 2

3 Table of Contents Abstract: Dell Virtual Remote Desktop Infrastructure Sizing Study... 5 Introduction Dell s VRD Solution Infrastructure Sizing Summary Experimental Setup and Workload Design Server and Storage Hardware: Desktop Virtual Machine Configuration: Performance Results High Performance User Knowledge Worker Structured Task Worker Summary and Suggested Guidelines

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5 Dell Virtual Remote Desktop Infrastructure Sizing Study End-to-End Computing Enterprise Solutions Engineering Dell Inc. Introduction The Virtual Remote Desktop (VRD) solution that uses Dell hardware with the VMware Virtual Desktop Infrastructure (VDI) application is the second offering from Dell in the flexible computing space. The Dell VRD solution addresses the need of customers who require alternate desktop architectures. In a VRD infrastructure, the user applications, data, and images are maintained by a data center administrator. Each desktop instance is run inside a Virtual Machine (VM) running on Dell PowerEdge servers running VMware ESX virtualization software. This white paper describes the sizing guidelines for configuring the backend infrastructure (ESX servers in particular) for a Dell VRD solution. 1.0 Dell VRD Solution The Dell VRD solution is built on Dell hardware and VMware VI3 and Virtual Desktop Manager (VDM) applications. The components of this solution using Microsoft Active Directory (AD) servers are shown in Figure 1. Enterprise desktops are hosted on VMware infrastructure and accessed by remote users through the VDM connection server. VDM connection server handles both the creation/provisioning of desktop VMs and the user connections to those VMs. The VMs run in a resource-isolated, secure environment and support both Microsoft Windows XP and Windows Vista 32-bit operating systems. AD authentication is performed when the user enters login information and password through the web access or VDM client. User policies and assignments are handled by the VDM server by polling the Microsoft AD server for user and group information to assign the appropriate VM. After passing authentication, the user s AD credentials are passed through to the target VM and an RDP connection is established. This solution provides Dell IT customers with centralized control over desktop computing resources and their data by hosting Figure 1: Active Directory (AD) VRD Solution 5

6 corporate desktops in enterprise hardware inside a datacenter. Users also gain the flexibility of being able to access their complete desktop environment from any location using more than one client. 2.0 Infrastructure Sizing Summary When sizing a VRD solution, the servers and storage that are required for an n-desktop scenario depends on a number of factors. On the user side, the desktop configuration (such as amount of memory, desktop resolution, OS settings) and user workloads (such as typing speeds, applications used, network access) play a significant role in determining how many desktops can be hosted on a single server. At the other end, the configuration of the Dell serverr that is hosting the desktops (such as number of CPUs, type of CPU, amount of memory) have to be sized appropriately to ensure that an optimal number of desktopss can run without performance degradation. To represent a range of desktop user scenarios, Dell Enterprise solutions engineers ran experiments using three types of workloads: structured task worker, knowledge worker, and high-performance user. A VRD solution is most suited for a knowledge worker scenario, and thereforee most of these experiments were performed generating sizing requirements for this workload. Structured task worker and high-performance users are includedd for comparison purposes, and for some customers, a VRD solution can be used to satisfy these users as well. Figure 2: CPU Load for PowerEdge R805 (4 cores) and PE 2950 (8 cores) Figure 2 shows the CPU load on two Dell PowerEdge servers running similar test scriptss that are used by VMware for VDI sizing efforts, which are documented in the white paper available at / In the study performed by VMware, the range of desktop VMs that could be supported per processor core ranged from six for heavy workloads to ten for light workloads. Dell engineers observed similar results during testing server usage and end-user performance expectations that were met when 6

7 configuring six to eight desktop VMs per CPU core for heavy and medium knowledge worker workloads. Figure 3 shows the execution time for a single iteration of the script on each VM when all VMs were running the workload simultaneously. The scripts were executed times on all desktop VMs to ensure that the run times did not deteriorate when compared to time taken when running a single desktop VM on an idle server. The execution time of the medium workload was approximately six minutes and 54 seconds. The heavy workload, which featured a faster typing speed (2000 wpm compared to 120 wpm for medium worker) took a shorter duration of six minutes to complete the same set of actions. Figure 3: Execution Time of Single Iteration of Knowledge Workerr script on Desktop VMs 3.0 Experimental Setup and Workload Design In order to size the backend infrastructure for a Dell VRD solution, engineers simulated end- The scripts can be compiled into executables that simulate a corporate desktop user s user desktop workloads using a general scripting and Windows GUI automation tool: AutoIT. actions, such as performing various operations on productivity applications. These scripts were compared to the client-server scriptss used by the VMware VDI sizing study as a sanity check. The AutoIT scripts are run on individual desktops and have a degree of randomness built into them so that the VMs are not all synchronized and doing the exact same operations at any given time. The operations performed by the knowledge worker are based on the VDI sizing paper from VMware VDI Server Sizing and Scaling. Operational steps performed by the knowledge worker occur in the following sequence: Perform these stepss in a loop sequence. 7

8 1. Start a PowerPoint application. Open a 5-MB presentation with automation and go through 50 slides. Close the PowerPoint application. 2. Start an Internet Explorer application. Browse three different web pages. Close the Internet Explorer application. 3. Start a command prompt and perform a directory listing. Close the command prompt. 4. Start a PowerPoint application. Open a 5-MB presentation with automation and go through 50 slides. Close the PowerPoint application. 5. Start an Excel application. Open an Excel file. Close the Excel application. 6. Start a PowerPoint application. Open a 5-MB presentation with automation and go through 50 slides. Close the PowerPoint application. 7. Start a Microsoft Word application. Type a one-page document. Close the Microsoft Word application. Performing a single iteration of these operations took approximately 5-7 minutes depending on the typing speed used. Typing speeds of 120 wpm and 200 wpm were used to gather multiple data points. The typical typing speed for experts is in the wpm range, and therefore these results represent a worst-case scenario for most customers. The BAPCO SYSmark 2007 performance metric application was used to represent a performance user and also to enable comparisons to customers with existing client hardware. Simple data entry tasks were performed to simulate a structured task worker. In addition, the AutoIT executable runs within the desktop VM and there is no interaction with external clients. Therefore, there is no end-user latency that is measured for this study and all the measurements are performed at the ESX server hosting the desktop VMs. 3.1 Server and Storage Hardware: Dell PowerEdge R805 (AMD Opteron Processor GHz, 16GB DDR2-667) o Software ESX Server 3i build Dell PowerEdge 2950 (Intel Processor E GHz, 32GB DDR2-667) o Software ESX Server 3i build Dell PowerVault MD3000 (15 x 146GB 15k RPM RAID-5 Array) 3.2 Desktop Virtual Machine Configuration: XP Desktop Single Virtual CPU, 384MB Memory, 10GB virtual disk Windows XP Professional with SP2 Windows Vista Desktop Single Virtual CPU, 1024MB Memory, 30GB virtual disk Windows Vista Business Edition 8

9 A Dell desktop machine was used as a test controller machine to launch tests on the desktop VMs, gather time stamps to measure script run times, and run power measurement software to gather power consumption of the Dell server hosting the desktop VMs. 4.0 Performance Results This section summarizes the results for the high-performance user, knowledge workerr and structured task worker workloads. 4.1 High Performance User SYSmark 2007 preview is a client benchmark from BAPCO ( that is used to measure and compare PC performance based on real world applications. Dell Solutions engineers chose a subset of the benchmark that reflects usage patterns of businesss users in the areas of video creation, e-learning and, office productivity. Figure 4 shows the performance results when running the benchmark on physical PCs and compares it to performance of a virtual desktop running inside a Dell PowerEdge R805 server with two dual-core Intel Xeon CPUs. Figure 4: SYSmark Performance on PCs and Virtual Desktop VMs The first bar shows the performance of a high-end PC equipped with a dual-core CPU and, as expected, the best performance was observed on this configuration. Performance of a single virtual desktop VM is 4% to 10% better than a physical PC with a single-core CPU. As the number of VMs on the PowerEdge 805v server is increased to 4% (one VM per core) and 8% (two VMs per core), a degradation in SYSmark benchmark performance occurred that ranged from 12% to 42% for video creation, which is the most computer-intensive workload among the three desktop VMs. 9

10 Figure 5: CPU Usage Running SYSmark on Desktop VMs Figure 5 shows the CPU usage when running the one to eight virtual desktop instances on the PowerEdge 805v server. When SYSmark is run on four VMs simultaneously, it saturates the CPU at 100% when executing the video creation benchmark. When running eight VMs, the CPU is saturated at 100% for longer periods of time and the workload takes longer to completee compared with the one-vm and four-vm benchmark runs. For a high-performance user with workload characteristics similar to SYSmark requiring very high system power, exceeding one VM per core will result in non-optimal performance. Each instance of SYSmark is observed to saturate a single CPU completely and will have to be sized accordingly. For this particular workload, used to reflect a high performance-user, a sizing guideline of one VM per CPU core (of the ESX server) is optimal. Going beyond that will exhaust ESX server resources and result in performance degradation to the end user. 4.2 Knowledge Worker The knowledge worker workload details and operational steps are describedd in section 3.0. Two typing speeds were used, 120 wpm and 200 wpm, to represent medium and heavy knowledge worker scenarios. The knowledge worker is a representation of a corporate desktop user that uses Microsoft PowerPoint, Word, and Excel applications to create and edit documents. The user also opened web pages and executed commands on the command prompt. Comparing Heavy and Medium Workload Scenarios Figure 6 illustrates the CPU and memory usage when running the heavy and medium knowledge worker workloads. The CPU load is plotted on the primary axis (blue line) and free memory is shown in the secondary axis (green line) as available MBytes of system memory. Time is represented on the X-axis. 10

11 Figure 6: CPU and Memory Usage for Heavy and Medium Knowledge Worker Workload The first spike for CPU load in the heavy worker chart occurs at 4:10 when all the VMs are powered on. As the scripts are started sequentially on a free desktop VM every 7 minutes (starting at 4:33), the CPU load is observed to increase sequentially till the 24th VM is started, which subsequently remains steady at a high state (starting at 6:30). When the VMs are all powered on at 4:04, the available memory is observed to drop from 15.4GB to 5.7GB since each VM is configured with 384MB of memory (total of 9.2 GB memory requirement for 24 VMs). The page-sharing optimization in ESX reclaims a majority of that memory. The available memory is observed to be at 11.1GB after a 15-minuteidle period. Once the scripts start executing, the memory usage is observed to increasee and another 2GB of system memory is used during the workload execution, increasing the amount of memory used to 6.3GB to run knowledge worker scripts on 24 desktop VMs. The ESX page sharing algorithm enables a savings of approximately 3GB of system memory since all the desktop VMs are using the same applications and operating system images. Similar CPU and memory trends are observed for the medium knowledge worker workload as well. Windows XP Professional SP2 vs. Windows Vista Business Edition This section compares knowledge worker workload execution on Windows XP Professional and Windows Vista Business edition. The minimum memory configuration requirements for the Windows XP edition are 256MB and 1GB for the Windows Vista Business edition. Therefore, the Windows XP desktop for medium and heavy workloads were configured with 384MB of system memory. The Windows Vista desktop VM was configured with a higher memory configuration of 1GB. When comparing the average CPU usage on both desktops, the results are similar (76% for XP and 74% for Microsoft Vista) when executing six desktop VMs per CPU core (total of 24 VMs). Since the memory requirements for Windows XP professional and Windows Vista Business desktopss differ significantly, the amount of system memory consumed was also significantly different when comparing the two types of desktop VMs. The PowerEdge R805 was configured with 16GB of memory; the 24 Windows XP desktop VMs (along with ESX) consumed approximately 6.5GB of memory; and the 24 Windows Vista desktop VMs used up approximately 13.3 GB of system memory. 11

12 Figure 7: CPU Usage and Memory Usage for XP Professional and Windows Vista Business Desktop VMs 4.3 Structured Task Worker Finally, Dell Solutions engineers simulated a structured task worker scenario in whichh the desktop user enters 900 random numbers into a Microsoft Excel worksheet (30 rows x 30 columns). The only application that is running on the desktop is Excel. As expected, the number of concurrent desktopss that can be hosted on the PowerEdge R805 server for this workload is higher than the previous two scenarios. Figure 8 shows the CPU and memory usage for multiple-structured task workers that were hosted on a single PowerEdge R805 server. The number of desktop VMs is incremented by 16 until it reaches a total of 64 VMs. 12

13 Figure 8: CPU Usage and Memory Usage for Structured Task Worker Scenario The average CPU usage when running 16 VMs (four VMs per CPU core) is 15% and the system memory used is approximately 5.5GB. As the desktops are running, more system memory is made available to the system due to transparent page sharing by the ESX server that frees up to 12GB while 16 desktop VMs are running the data entry workload. At 7:41, 16 additional VMs are powered on (from suspend mode), whichresults in a CPU usage spike of up to 60%. Once all the VMs are powered on, the average CPU usage, when running the structured task worker on 32 concurrent VMs, increases to 31% and available system memory drops to 8GB during the run period for 32 VMs. After 20 minutes at 8:02, an additional 16 VMs are powered on and the workload runs on 48 desktop VMs, which increases the average CPU usage to 61% and drops the available system memory to 2.4GB. The CPU usage almost spikes to 100% when the final 16 VMs are powered on while running 48 VMs. When the workload runs on the remaining 16 VMs (increasing the total desktop VMs running to 64), the average CPU usage increases to 79% and available memory is as low as 1.8GB during this period. The CPU usage volatility is more pronounced during the 48 and 64 desktop VM runs since the scheduling overhead on the ESX server is extremely high due to the large number of VMs. 5.0 Summary and Suggested Guidelines Figure 9 shows the range of desktop virtual machines that were hosted on the PowerEdge R805 based on the workload profile used in this study. For a high-performance user, there was a negative impact on overall performance when more than four VMs were running on the server. 13

14 CPU Utilization (%) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 52% 1 VM per Core High Performance User 86% 84% 6 desktop VMs per Core Knowledge Worker Heavy 8desktop VMs per Core Knowledge Worker Medium 79% 16 desktop VMs per Core Structured Task Worker Figure 9: Recommended Desktop Virtual Machines Based on Available CPU Cores For a knowledge worker scenario, running 24 to 32 VMs resulted in about 85% of CPU usage and no degradation in end-user performance. For a structured task worker scenario, up to 64 VMs were hosted on a single server with no negative impact to desktop-user performance. When performing capacity planning for a VDI deployment, the end-user workload will have a large impact on the number of ESX servers required to host the remote desktop images inside the data center. Similar analysis needs to be conducted using a representative desktop workload of the users supported by the Virtual Remote Desktop solution. 14