During my testing VMware ESXi 4.1 which is the last version currently, I’ve installed it on two VM on my VMware Workstation 7.1 which supporting ESX 4.0 as guest OS.
The system I’m used on my working place have Intel E5300 CPU, 2GB DDR2 Memory and running Windows XP SP3.
There are some good reference for installing VMware ESX/ESXi 4.x on the VMware Workstation 7.x on the internet, so let me just point to two of them.
How-to Install ESX 4 inside VMware Workstation 7 video and Running VMware ESXi 4 / vSphere in VMware Workstation – VIDEO.
Well, According to VMware Workstation 7.x “New Virtual Machine Wizard”, the minimum required memory for VMware ESX 4.x is 2GB and it seems for running two VMware ESX 4.x each with 2GB memory as guest OS on the Windows XP as host OS, at least 4GB memory is required!!
This can be tested very easily, just install first guest OS and after finishing the installation, just power it off or put it in the suspend mode and install the second one, then power on/resume the first one.
In this case the system would use almost all memory resources as it can see and system would be freeze.
For preventing this, there’s a solution which will affect on performance of both host and guest os (better for host and can be worst for guest) but as long as this is just a lab and the number of the VMware ESX/ESXi is important for some test so it would be ok, just in case of testing and using two guest OS with 2GB.
By default, VMware Workstation allows some part of guest OS to be swapped and by changing this option most of guest OS would be swapped or all of it would be use physical memory.
In this condition (lack of memory on the host), it can be change to using swap for most of guest memory.
This option can be found under “Memory” tab of “Preferences” for VMware Workstation.