VMware vSAN is a hyperconverged solution that creates a shared datastore from locally attached disks within each server of the cluster. As such, you do not need to buy dedicated SAN hardware. The whole cluster IS the shared storage, as each server within the cluster participates with its local disks.

However, it is not easy to choose a server that meets the requirements. Not all servers are compatible with vSAN and allow you to size accordingly so you can meet your IOPS needs for your virtual machines (VMs) and your applications.

VMware has solved these difficulties and introduced vSAN ReadyNodes, which are x86 servers available from all leading server vendors. These servers are preconfigured, tested, and certified for VMware vSAN. There are many vendors now and many different sizes that can be chosen for vSAN Hybrid or the vSAN All-Flash version.

The ready nodes are optimally configured for vSAN with the number of CPUs, memory, network, I/O controllers and storage (SSDs, HDDs, or flash devices) needed to run the vSAN at optimal performance.

There is a free online tool from VMware that allows you to pick the vendor and the type of node you need. You can then shop via traditional hardware channels and find the exact server model.

The online tool gives you flexible options to build a hyperconverged infrastructure and run VMware vSAN. It allows you to pick the vSAN version, select Hybrid or All-Flash, and select a hardware manufacturer and model.

vSAN ReadyNode Sizer

Prior to running the configurator, VMware recommends running vSAN ReadyNode Sizer, a tool that enables you to size vSAN and get a report showing you the CPUs and CPU cores, memory, and storage you'll need for each host.

The tool is accessible online; however, you'll need to create a free VMware account. After that, you're guided through a workload profile creation matching your on-prem environment.

A workload profile is a profile where the tool gathers information about the workloads you're running, whether for VDI, general purposes, or database workloads you're planning.

If you have multiple workloads running, it's better to create multiple profiles that add up to form a complete picture of the demands of your environment. After creating one profile for, let's say, VDI, you can create a second one for DB workloads, and then a third one where you specify your general-purpose workloads.

You're asked about the number of VMs, storage capacity for each VM, number of CPUs, and RAM. In addition, the tool gathers the host failure protection (1, 2, or 3) and fault tolerance method (RAID-5, for example).

The IO profile is another section where you can specify the workloads and IO access pattern (random or sequential). Below is an example of the local workload profile:

Creation of a local profile for vSAN ReadyNode Sizer

Creation of a local profile for vSAN ReadyNode Sizer

Once you have all your profiles created and registered, you can proceed with the next section, which has a number of important configuration options.

You can see the Recommendation section, where in my case, I have four ESXi servers with 15 DB VMs in my demo cluster. You can see the capacity used, vSAN version, effective usage capacity, licensing recommendations, and per-node configuration.

In the per-node recommendation section, I can see that AF-6 or AMDAF-6 are the recommended nodes. We'll see later that those are "All-Flash" nodes from Intel or AMD.

vSAN ReadyNode Sizer

vSAN ReadyNode Sizer

If we zoom into the right-hand side, we have resource utilization statistics. It is possible to modify the number of cores, the number of IOPS required, the capacity, and the memory on the fly. The capacity includes growth factors and operations reserves.

Resource utilization statistics and possible modifications

Resource utilization statistics and possible modifications

When clicking the IOPS or Capacity sections, the system gives you a choice as to whether you want to grow the number of hosts or disk groups.

As you know, you can grow capacity or IOPs within your vSAN cluster in two different ways:

  • Add more disk groups
  • Add more hosts

The disk group comprises one Flash disk and at least one or up to seven capacity (HDDs or Flash) devices (for the "All-Flash" vSAN version).

Grow capacity or IOPS by adding additional disk groups or nodes

Grow capacity or IOPS by adding additional disk groups or nodes

As a result, we can have a look at the ReadyNode recommender section. We can see that we can further choose whether we want ESXi to be preinstalled.

As a guideline, we have nodes AF-6 and AMD-AF6 with 23 TB raw capacity per node and six capacity drives.

You might ask why we don't see any results. This was intentional because I did not want to favor one vendor over another. I picked the "Asustek" vendor, which does not have a node that matches my requirements.

ReadyNode Recommender with or without ESXi preinstalled

ReadyNode Recommender with or without ESXi preinstalled

Once we know which type of node we need and what the storage requirements are, we can proceed with the vSAN ReadyNode Configurator.

vSAN ReadyNode Configurator

Once we have gone through the sizer, we can now use the main tool—the Configurator. You can access vSAN ReadyNode Configurator here. Here, the choice is very simple because we already know:

  • Which version of vSAN we want to run
  • Which profile we need to select (AF-6 series)
  • We'll need to pick an OEM manufacturer (I'll pick one at random, let's say Fujitsu.)
  • Select model

Note that we can still click the Let Us Help button (on the right) and let VMware adjust what's needed.

vSAN ReadyNode Configurator

vSAN ReadyNode Configurator

The Let Us Help button opens another window, allowing us to adjust cores, memory, and usable capacity as well as IO intensity.

vSAN ReadyNode Profile Wizard

vSAN ReadyNode Profile Wizard

Then, by clicking the OEM (in our case Fujitsu, but this can be any other vendor), we'll have a list of models available with the right configuration.

Let's say we want NVMe storage for the caching tier. From the same page, we can download the configuration as PDF, contact sales, or request an assessment.

Select model and next step

Select model and next step

This is it. We have all the necessary information. We were able to use this tool to help us choose the right size for our vSAN nodes. The IOPS requirements are included, so you should run the tool prior to going to this portal. There are tools allowing you to measure what your applications are running, and which kind of IOPS they're generating.

Final words

VMware vSAN Node Configurator and vSAN ReadyNode Sizer are both complementary tools that enable you to know and help you choose the right vSAN ReadyNode type, with the correct number of CPU cores, memory, and storage by keeping in mind your resiliency requirements as well.

VMware vSAN has specific requirements for hardware and firmware/BIOS combinations. If you make an error and pick the wrong hardware, you might end up with bad performance and incompatible hardware that is unable to run workloads from your environment.

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When planning the step forward and moving from dedicated SAN hardware into a vSAN environment, this tool makes the admin's life much easier as the performance is already tested and predictable.

1 Comment
  1. Curtis G Mezger 2 years ago


    vSAN is great for shoe-string budgets, and other uses on the vSphere host, but one draw back if you are using vRealize Automation (vRA) and vSAN is vRA will not respect, or acknowledge vSAN storage so the reservation policy built in in vRA could/would show that you may be almost out of storage.
    I learned this through a support ticket with vRA engineers, and the engineer told me, well then don’t use vSAN and that is verbatim. I wound up increasing the amount of storage that vRA thought I had by a crap-load.

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