VMware vSAN is a powerful software defined storage solution. It is changing the way organizations design and manage storage found in VMware vSphere environments. It provides a robust feature set that enables VMware vSphere administrators to be agile, flexible, and scale up and out very easily. VMware vSAN includes a powerful feature and functionality set for VMware administrators as well provides an architecture that is resilient to failure. However, what are some common VMware vSAN mistakes that are made which can jeopardize both the performance and health of a VMware vSAN installation? Let’s take a look at a few common mistakes that administrators make and how these can be avoided in keeping with VMware best practices.

VMware vSAN Common Mistakes

There are critical best practices that vSphere administrators want to make sure they follow in any VMware vSAN implementation. This can make the difference between a successful vSAN implementation and one that can put your data at risk. We will take a look at the following mistakes and the best practices that could have avoided those mistakes.

  • Using uncertified, commodity hardware
  • Failing to configure the network properly
  • Using traditional benchmark utilities
  • Failing to use the built-in online vSAN health tests
  • Failing to understand new backup considerations

Using Uncertified, Commodity Hardware

It goes without saying that you should always make use of hardware that is supported with any solution. However, some make the mistake of thinking that VMware vSAN can make use of “anything” when it comes to storage hardware. While those who run a VMware home lab can attest to the fact that VMware vSAN does a great job of just “working” when it comes to provisioning and making use of storage hardware (ssds, hdds, storage controllers), this can be a dangerous thing to do with production environments. You always want to make sure your hardware is certified for use with VMware vSAN. A great resource for vSAN and all other VMware products in determining compatibility is the VMware Compatibility Guide that allows verification of hardware with VMware products and solutions.

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VMware Compatibility Guide

Always check hardware compatibility using the VMware Compatibility Guide

Examples of common issues with commodity hardware include not utilizing SSDs that have power-loss protection or utilizing storage controllers that are not able to meet the queue length demands that vSAN requires. Using the vSAN health checks in vCenter provides a good way to see if you are using hardware that is not on the HCL.

VMware vSAN Health module

The VMware vSAN Health module checks for Hardware compatibility

Failing to Configure the Network Properly

As with most storage infrastructure, the network is a critically important component of VMware vSAN. A common VMware vSAN mistake that can be made with a VMware vSAN implementation is an improperly configured network. There are a number of best practices when considering the network configuration with VMware vSAN. Configuring the network according to these best practices allows for a vSAN solution that performs well as is resilient as designed. Below are a number of VMware vSAN network configuration best practices:

  • Use dedicated 10 gig (all flash) or 1 gig (hybrid) links
  • While you can use VSS switches, it is preferable to use DVS switches. This allows for several advantages when it comes to standardizing the network configuration between hosts, utilizing NIOC, and gives more options when it comes to supported load balancing technologies
  • Use multiple physical NICs – Always have a failover NIC configured
  • Utilize Jumbo frames – Utilizing jumbo frames ensures the best performance for the lowest CPU cost per host. However, there may be situations where jumbo frame configuration isn’t possible due to the underlying network reconfiguration required
  • Witness Host network configuration issues – The witness host is the component of the VMware vSAN stretched or two-node cluster that allows for a witness component to maintain quorum in the vSAN cluster

Failing to follow the above VMware vSAN networking best practices can lead to performance issues or host isolation scenarios where data may be in jeopardy.

Using Traditional Benchmark Utilities

One of the first things that most vSphere administrators will want to do when standing up any storage solution is run a benchmark on it. VMware vSAN is generally no exception. Administrators generally want to verify they are getting the IOPs they had accounted for during the design phase of the solution. However, a common mistake when benchmarking HCI solutions such as VMware vSAN is utilizing legacy disk benchmarking utilities. Making use of legacy benchmarking disk utilities does not account for the distributed architecture of the vSAN deployment. Legacy tools are designed to test the IOPs of a single disk generally speaking. Without making use of multiple VMs with potentially multiple disks spread across the multiple hosts in a vSAN deployment, you really are not able to see the true potential of a VMware vSAN implementation. Rather than making the mistake of utilizing legacy disk benchmarking utilities, use a purpose-built utility such as VMware HCI bench. HCI bench is designed to properly benchmark an HCI solution such as VMware vSAN.

HCI Bench

HCI Bench testing architecture (courtesy of VMware)

Failing to Use vSAN Online Health Tests

One of the great features of VMware vSAN is the built-in health checks that vSphere administrators have access to in the vSAN monitoring section of the vSphere web client. The software-defined approach brings all the component checks into a “single pane of glass” view of the VMware vSAN environment. This includes checks on the following:

  • Hardware compatibility
  • Network configuration
  • Storage health
  • Physical disks
  • Data check
  • Cluster
  • Stretched cluster

It would be a tremendous mistake on the part of a vSphere administrator to not utilize this powerful tool in analyzing VMware vSAN health and performance. It proactively keeps a check on overall VMware vSAN health.

Additionally, the Check with Online Health option allows for checking the environment against the latest VMware vSAN KBs and such. So, there is really no excuse for knowing the health of your VMware vSAN environment. Don’t make the mistake of not making use of these great tools that are built-in, right out of the box.

Retest with Online health option

Using the Retest with Online health option

Failing to Understand New Backup Considerations

No matter what underlying storage solution you are making use of, having backups of your data is imperative! VMware vSAN is no exception to this. With the new HCI architecture that powers VMware vSAN, there are some backup considerations to be made when utilizing VMware vSAN. Failing to take these into account can lead to unexpected backup challenges.

VMware vSAN is able to take advantage of the vSphere Storage and Data Protection APIs the same as traditional vSphere storage so most backup solutions are able to interact with VMware vSAN the same as previous technologies. However, there are a couple of items that administrators need to take note of concerning vSAN and backups.

  • SAN Transport mode is not supported
  • Since virtual machines backed up can take advantage of Storage Policy-Based Management or SPBM, vSphere administrators will want to check their backup solution to make sure it can work with SPBM. If a backup solution does not interact with SPBM policies, these will need to be reapplied after virtual machines are restored

For administrators to not make sure their backups are supported properly with VMware vSAN would be a mistake and could lead to data loss.


VMware vSAN is a powerful solution. However, vSphere administrators need to make sure they are following VMware recommended best practices when implementing a vSAN solution. As shown above, there are many VMware vSAN common mistakes that can lead to poor performance and stability issues. Data loss can ultimately result from mistakes being made with implementing a vSAN solution. By covering the bases and following best practices and performance guidelines, vSphere administrators will ultimately have a powerful distributed storage system that will be well suited to run business-critical applications.

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