Improved performance and user densities with Dell EMC Ready Solutions for VDI, powered by 2nd Generation Intel
Mon, 03 Aug 2020 16:17:48 -0000
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Improved performance and user densities with Dell EMC Ready Solutions for VDI, powered by 2nd Generation Intel Xeon Scalable processors
Published on May 15, 2019 by Anand Johnson, Principal Engineer
Performance is one of the key factors required for a successful Virtual Desktop Infrastructure (VDI) deployment. It is often challenging for IT teams to measure performance and perform capacity planning for their environments without proper benchmarking tests. With the discovery of the Spectre, Meltdown, and L1 Terminal Fault vulnerabilities in 2018, VDI support teams wanted to know the potential negative performance impact these vulnerabilities might have on their environments. A VMware benchmark study performed in August 2018 found that VDI systems patched for L1TF\Foreshadow had a performance degradation of up to 30%.
Spectre, Meltdown, and L1 Terminal Fault are all types of side-channel vulnerabilities, meaning that they use certain design characteristics of modern-day processors, such as timing information, power consumption, electromagnetic leaks, and emitted sounds to gain information for use in the attack. Mitigations provided in the form of operating system patches, hypervisor patches, or microcodes address these vulnerabilities indirectly. However, hardware-level fixes are preferable because addressing these vulnerabilities from the kernel- or software-level is likely to have a negative impact on system performance.
The recently announced 2nd Generation Intel Xeon Scalable processors (Cascade Lake) include fixes in the silicon for Spectre (variant 2), Meltdown (variant 3), and L1 Terminal Fault side-channel methods. These fixes mean that the new processors are expected to provide a better performance than first-generation Intel Xeon Scalable Processors (Skylake) or other previous generation processors, which still require software-level fixes to protect against side-channel vulnerabilities. Cascade Lake processors also come with an improved architecture and higher thermal efficiency that boosts the performance of the systems.
Dell EMC-Ready Solutions for VDI on both VxRail and vSAN ReadyNodes are now available with 2nd Generation Intel Xeon Scalable Processors (Cascade Lake). Cascade Lake processors have more benefits beyond better security, which you can read about here. The Dell EMC VDI engineering team performed an impressive comparison test between Intel Xeon Gold 6248 processor (Cascade Lake) and the previous generation’s Intel Xeon Gold 6138 processor (SkyLake) with the results described below. I think that’s enough of an introduction; let’s get to the meat of the testing.
Test environment
The Dell EMC VDI engineering team performed tests with Login VSI, an industry standard for benchmarking VDI workloads. The following workloads were tested:
· Knowledge Workload running on VMs configured with 2 vCPU and 4 GB RAM
· Power Workload running on VMs configured with 4 vCPU and 8 GB RAM
The test bed environment was a 3-node cluster of VxRail V570F that was optimized for VDI workloads. The cluster was configured and tested with Skylake processors and then with Cascade Lake processors. Environment configuration was:
- PowerEdge R740xd servers
*Intel Xeon Gold 6138, 2 x 20-core, 2.0 GHz processors (Skylake testing)
*Intel Xeon Gold 6248, 2 x 20-core, 2.5 GHz processors (Cascade Lake testing)
*768 GB memory (24 x 32 GB @ 2400 MHz) (Skylake testing)
*768 GB memory (24 x 32 GB @ 2666 MHz) (Cascade Lake testing)
- vSAN hybrid data store using an SSD caching tier
- VMware ESXi 6.7 hypervisor
- VMware Horizon 7.7 VDI software layer
Compute virtual machines are Windows 10, 64-bit, version 1803. One of the VxRail cluster nodes hosted both management and compute virtual machines. The other two nodes were dedicated for workload compute. Figure 1 shows the main components.
Figure 1: Horizon VDI test environment: Main components
For more details about the environment, configuration, and testing methodology see the Design and Validation Guides under "Designs for Vmware Horizon on VxRail and vSAN Ready Nodes" on our VDI Info Hub for Ready Solutions website.
The threshold for CPU, Memory, and Network Usage was set to a conservative 85%. A 20ms Disk Latency threshold was also set. The consensus of the team based on field experience is that if these thresholds are exceeded, the user experience might noticeably degrade.
User density and resource usage metrics
Refer to Figure 2 for the user density results obtained from the Cascade Lake vs. Skylake testing for both the Login VSI power and knowledge workloads.
Figure 2: User Density Per Compute Node
Cascade Lake processors outperformed Skylake processors in user density per compute node by approximately 62% for the knowledge workload and by 54% for the power workload. The CPU steady-state average stayed in the range of 84-87% for all the test cases, which is close to the threshold parameter set during test design. Memory, network usage, and disk latency showed no sign of causing bottlenecks over the duration of the tests. For a detailed analysis report and more resource usage metric results, see the Validation Guide under "Designs for VMware Horizon on VxRail and vSAN Ready Nodes" on our VDI Info Hub for Ready Solutions website.
Login VSI Overview
You can find background information about Login VSI analysis on the Login VSI website. Refer to Figure 3 for Login VSI response time metrics for each test case.
Figure 3: Login VSI user experience summary
VSIBase rating for Cascade Lake testing is “very good,” (0-799ms) and the rating for Skylake testing is “good.”(800-1199ms).VSIBase is the response of the system before actually loading the system with any user sessions. A lower VSIBase value indicates that the performance of the base image is better.
VSIMax was not reached during any of the tests. With CPU reaching a threshold of 84-87%, we noticed that VSIMax Average (the average response time for the whole system) was in the range of 1000-1100ms for all tests. VSIThreshold, which is the saturation point of the environment, was never reached. VSIMax shows the number of sessions that can be active on a system before the system is saturated. Considering the importance of the user experience, it is best not to exceed a threshold of 85% for average CPU utilization during testing. Therefore, the recommended density from our testing is constrained by the thresholds we set for system resources during test design.
Lastly, there were no “stuck sessions” reported during testing, indicating that the system was not overloaded at any point in time.
Our engineering testing suggests that if performance and scalability are currently or expected to be an issue in your environment, upgrading to Cascade Lake processors might help you. Each environment is unique, so we recommend that you benchmark your environment before you make any major changes to your production system to minimize any potential negative performance impacts. With proper benchmarking and by leveraging a tested and validated solution like Dell EMC Ready Architectures for VDI, the performance of your VDI environment does not have to be a challenge. For details about Dell EMC benchmark tests, refer to Ready Architectures for VDI on the VDI Info Hub for Ready Solutions website.
In the next blog, we will explore NVIDIA GPUs and vGPU software as part of the Dell EMC Ready Solutions for VDI.