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vSAN Performance Diagnostics Now Shows “Specific Issues and Recommendations” for HCIBench

By Amitabha Banerjee and Abhishek Srivastava

The vSAN Performance Diagnostics feature, which helps customers to optimize their benchmarks or their vSAN configurations to achieve the best possible performance, was first introduced in vSphere 6.5 U1. vSAN Performance Diagnostics is a “cloud connected” feature and requires participation in the VMware Customer Experience Improvement Program (CEIP). Performance metrics and data are collected from the vSAN cluster and are sent to the VMware Cloud. The data is analyzed and the results are sent back for display in the vCenter Client. These results are shown as performance issues, where each issue includes a problem with its description and a link to a KB article.

In this blog, we describe how vSAN Performance Diagnostics can be used with HCIBench and show the new feature in vSphere 6.7 U1 that provides HCIBench specific issues and recommendations.

What is HCIBench?

HCIBench (Hyper-converged Infrastructure Benchmark) is a standard benchmark that vSAN customers can use to evaluate the performance of their vSAN systems. HCIBench is an automation wrapper around the popular and proven VDbench open source benchmark tool that makes it easier to automate testing across an HCI cluster. HCIBench, available as a fling, simplifies and accelerates customer performance testing in a consistent and controlled way.

Example: Achieving Maximum IOPS

As an example, consider the following HCIBench workload that is run on a vSAN system:

Number of
VMs
Number of
Disks (vmdks)
to Test
Number of
Threads/Disk
Working Set
Percentage
Block Size Read/Write
Percentage
Randomness
Percentage
1 10 1 100 4 KB 0/100 100

If the goal is to achieve maximum IOs per second (IOPS), vSAN Performance Diagnostics for this workload yields the result shown in figure 1.

Figure 1

In this example, vSAN Performance Diagnostics reports, “The Outstanding IOs for the benchmark is too low to achieve the desired goal”. Here we can see that the feedback from vSAN Performance Diagnostics tells us about the problem, and a possible solution recommends that we increase the number of outstanding IOs to a value of 2 per host. The linked “Ask VMware” article explains this issue and what we must do with the benchmark in more detail.

The new HCIBench Exceptions and Recommendations feature removes the need to read through a KB article by precisely mapping recommendations to one (or more) configurable parameters of HCIBench.

Now let us check how vSAN Performance Diagnostics works with vSphere 6.7 U1, which has access to this new feature (figure 2).

Figure 2

Now we can clearly see an exact issue in our HCIBench workload configuration that provides the precise recommendation to resolve this issue with the message: “Increase number of threads per disk from 1 to 2”.

Let us monitor the current write IOPS generated by the benchmark for our reference. We go to Data Center–>Cluster–>Monitor–>vSAN–>Performance (figure 3).

Figure 3

Now, as part of the evaluation, we apply the recommendation generated by vSAN Performance Diagnostics and check its impact. We now run the new HCIBench workload configuration with 2 threads per disk and the following parameters:

Number of
VMs
Number of
Disks (vmdks)
to Test
Number of
Threads/Disk
Working Set
Percentage
Block Size Read/Write
Percentage
Randomness
Percentage
1 10 2 100 4KB 0/100 100

After the benchmark completes, we use vSAN Performance Diagnostics again to see if we can now achieve the required goal of maximum IOPS. The result from Performance Diagnostics now shows “No Issues were found”, which means that we are achieving good IOPS from the vSAN system (figure 4).

Figure 4

Now, as part of actual verification, we can see the change in IOPS after applying the recommendation. From figure 5 below (screenshot from Data Center–>Cluster–>Monitor–>vSAN–>Performance), we can clearly see that there is a 25-30% increase in IOPS after applying the recommendation, which verifies that it helped us achieve our goal.

Figure 5

We believe that this feature will be very useful for customers who want to tune their HCIBench workload for a desired goal.

Prerequisites

  • Please note that this feature is currently integrated with HCIBench 1.6.7 or later.
  • This feature is available for vSphere 6.7 U1 and newer releases. It will not be available to patch releases of vSphere 6.7.