VDI Performance Benchmarking on VMware Virtual SAN 5.5

In the previous blog series, we presented the VDI performance benchmarking results with VMware Virtual SAN public beta and now we announced the general availability of VMware Virtual SAN 5.5 which is part of VMware vSphere 5.5 U1 GA and VMware Horizon View 5.3.1 which supports Virtual SAN 5.5. In this blog, we present the VDI performance benchmarking results with the Virtual SAN GA bits and highlight the CPU improvements and 16-node scaling results. With Virtual SAN 5.5 with default policy, we could successfully run 1615 heavy VDI users (VDImark) out-of-the-box on a 16-node Virtual SAN cluster and see about 5% more consolidation when compared to Virtual SAN public beta.


To simulate the VDI workload, which is typically CPU bound and sensitive to I/O, we use VMware View Planner 3.0.1. We run View Planner and consolidate as many heavy users as we can on a particular cluster configuration while meeting the quality of service (QoS) criteria and we define the score as VDImark. For QoS criteria, View Planner operations are divided into three main groups: (1) Group A for interactive operations, (2) Group B for I/O operations, and (3) Group C for background operations. The score is determined separately for Group A user operations and Group B user operations by calculating the 95th percentile latency of all the operations in a group. The default thresholds are 1.0 second for Group A and 6.0 seconds for Group B. Please refer to the user guide, and the run and reporting guides for more details. The scoring is based on several factors such as the response time of the operations, compliance of the setup and configurations, and other factors.

As discussed in the previous blog, we used the same experimental setup (shown below) where each Virtual SAN host has two disk groups and each disk group has one PCI-e solid-state drive (SSD) of 200GB and six 300GB 15k RPM SAS disks. We use default policy when provisioning the automated linked clones pool with VMware Horizon View for all our experiments.


CPU Improvements in Virtual SAN 5.5

There were several optimizations done in Virtual SAN 5.5 compared to the previously available public beta version and one of the prominent improvements is the reduction of CPU usage for Virtual SAN. To highlight the CPU improvements, we compare the View Planner score on Virtual SAN 5.5 (vSphere 5.5 U1) and Virtual SAN public beta (vSphere 5.5).  On a 3-node cluster, VDImark (the maximum number of desktop VMs that can run with passing QoS criteria) is obtained for both Virtual SAN 5.5 and Virtual SAN public beta and the results are shown below:


The results show that with Virtual SAN 5.5, we can scale up to 305 VMs on a 3-node cluster, which is about 5% more consolidation when compared with Virtual SAN public beta. This clearly highlights the new CPU improvements in Virtual SAN 5.5 as a higher number of desktop VMs can be consolidated on each host with a similar user experience.

Linear Scaling in VDI Performance

In the next set of experiments, we continually increase the number of nodes for the Virtual SAN cluster to see how well the VDI performance scales. We collect the VDImark score on 3-node, 5-node, 8-node, 16-node increments, and the result is shown in the chart below.


The chart illustrates that there is a linear scaling in the VDImark as we increase the number of nodes for the Virtual SAN cluster. This indicates good performance as the nodes are scaled up. As more nodes are added to the cluster, the number of heavy users that can be added to the workload increases proportionately. In Virtual SAN public beta, a workload of 95 heavy VDI users per host was achieved and now, due to CPU improvements in Virtual SAN 5.5, we are able to achieve 101 to 102 heavy VDI users per host. On a 16-node cluster, a VDImark of 1615 was achieved which accounts for about 101 heavy VDI users per node.

To further illustrate the Group A and Group B response times, we show the average response time of individual operations for these runs for both Group A and Group B, as follows.


As seen in the figure above, the average response times of the most interactive operations are less than one second, which is needed to provide a good end-user experience. If we look all the way up to 16 nodes, we don’t see much variance in the response times, and they almost remain constant when scaling up. This clearly illustrates that, as we scale the number of VMs in larger nodes of a Virtual SAN cluster, the user experience doesn’t degrade and scales nicely.


Group B is more sensitive to I/O and CPU usage than Group A, so the resulting response times are more important. The above figure shows how VDI performance scales in Virtual SAN. It is evident from the chart that there is not much difference in the response times as the number of VMs are increased from 305 VMs on a 3-node cluster to 1615 VMs on a 16-node cluster. Hence, storage-sensitive VDI operations also scale well as we scale the Virtual SAN nodes from 3 to 16.

To summarize, the test results in this blog show:

  • 5% more VMs can be consolidated on a 3-node Virtual SAN cluster
  • When adding more nodes to the Virtual SAN cluster, the number of heavy users supported increases proportionately (linear scaling)
  • The response times of common user operations (such as opening and saving files, watching a video, and browsing the Web) remain fairly constant as more nodes with more VMs are added.

To see the previous blogs on the VDI benchmarking with Virtual SAN public beta, check the links below:


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