I was recently chatting with a fellow colleague who asked an interesting question about the memory overhead between running vSAN Original Storage Architecture (OSA) versus the new vSAN Express Storage Architecture (ESA) from a VMware Homelab perspective. I honestly did not know the answer as I am only using vSAN OSA for my personal homelab. I was curious myself, especially its implicationn on small form factor (SFF) systems which typically max at out 64GB of memory.
Today, vSAN ESA is only officially supported when using vSAN ESA Ready Nodes which are all listed in the vSAN ESA HCL and the minimum amount of memory is 512GB. For the best possible experience and supported configurations, customers should only use approved vSAN ESA hardware and the use of any other systems will not yield the same benefits nor outcomes. As an aside, a fantastic resource for all things vSAN ESA can be found on the vSAN ESA TechZone page, which I highly recommend bookmarking as there is a lot of in-depth technical resources and collateral.
Disclaimer: This is not officially supported by VMware and is purely for educational purposes, use at your own risk.