There are many limitations between Free and paid version so even if you are runing a free esxi and as many as you want you will not be able to utilize them without a license and you will face many problems like :
- No storage APIs for the free version (they are there, but not enabled, maybe?), which means you cannot use Veeam, Unitrends, AppAssure, etc.
- Without vCenter Server (enabled with licensed version), moving guests between hosts takes a while. You can use 3rd party products to speed things up a little bit, but you are still having to download the vmdk from one host to storage (your laptop, or a network storage device), then upload the vmdk to the 2nd host. There is no direct host to host migration path in the free version.
Now, once you get knee-deep into server visualization and start looking at how much of a game changer it is between recovery methods over physical boxes, you will start thinking that vMotion, vStorage, SANs, and High Availability are definite things to look into. These are only enabled in the higher dollar licensed versions of ESXi (i.e., not Essentials).
Check the feature list :
Best regards
Yours, Oscar