A default amount of RAM is configured based on the selected guest OS. The specified RAM is the memory the OS will present to its system and it's also the maximum amount of RAM the VM can claim from the physical memory installed on the host.

Memory optimization techniques remain the same as the previous version, with a big change, starting from vSphere 6.0, in Transparent Page Sharing (TPS); page sharing is enabled by default within VMs (intra-VM sharing), but is enabled between VMs (inter-VM sharing) only when those VMs have the same salt value (described in the next section). This change was made to ensure the highest security between VMs. For more information, see KB 2080735—Security considerations and disallowing inter-Virtual Machine Transparent Page Sharing at https://kb.vmware.com/kb/2080735.

In vSphere 6.5, a VM supports a maximum of 6,128 GB of RAM (with the latest virtual hardware versions).