Thursday, July 15, 2021

vSAN Capacity and Performance Sizer

VMware vSAN is enterprise production-ready software-defined storage for VMware vSphere. After several (7+) years on the market, it is a proven storage technology especially for VMware Software-Defined Data Centers aka SDDC.   

As a seasoned vSphere infrastructure designer, I had a need for vSAN sizer I would trust and that was the reason to prepare just another spreadsheet with my own calculations. There are multiple VMware official vSAN and VxRail sizers, however, it is always good to have your own based on your understanding of underlying technology. It is not only about vSAN software, but also about vSphere/vSphere HA Cluster details (Admission Control HA Redundancy versus vSAN Data Protection within Storage Policy) and hardware related details like the performance difference between NAND Flash and Intel Optane Flash, NAND asymmetric read/write performance, etc. 

If you are looking for an official vSAN Sizer, go to

Here is the link to my UNSUPPORTED "vSAN Capacity and Performance Sizer".

Usage Instructions:

Download the excel file from the link above and start to play with yellow cells to plan your capacity and performance design.

What's unique about my vSAN sizer?

  • Detailed storage capacity calculation allowing to consider vSphere HA Admission Contro
  • Storage performance sizing for various workload pasterns with 64 kB I/O size, which is IMHO typical I/O size average in an enterprise environment
    • I/O Size 64 kB, 100% read, 100% random
    • I/O Size 64 kB, 70% read, 100% random
    • I/O Size 64 kB, 50% read, 100% random
    • I/O Size 64 kB, 30% read, 100% random
    • I/O Size 64 kB, 20% read, 100% random
    • I/O Size 64 kB, 0% read, 100% random

Disclaimer: PERFORMANCE SIZING IS VERY TRICKY!!! Over the years, I used this excel for various vSphere designs and sometimes even validated capacity and performance estimations. Based on the test results, I was tuning the calculations and parameters. However, this is always just an estimation that has to be always validated by vSphere designer responsible for a particular design.

Hope you will find this tool useful. The only ask for anybody who will use the spreadsheet for capacity and mainly performance estimations, please, give me the feedback if calculated results were close to capacity and mainly the performance you observed during your testing before putting the infrastructure into production. We all do perform test plans before production usage, right? :-) And we all know that VMware has a great synthetic storage performance test tool called HCI Bench, do not we?

Share and collaborate, this is the way we live in the VMware community!

Use comments below the blog post for further discussions.