Minimum specification required as following

• 2GB RAM
• 1vCPU
• 1 or 2 dedicated physical NICs depending on if you’re spanning or in-line. 

Check out the following link to learn more about the Virtual Appliance deployment.
https://community.sinefa.com/hc/en-us/articles/201112907-Quick-Start-Guide-VMware-ESX-ESXi-vSphere