vSphere 5.0 New *.vswp file

Virtual Machine swap files have been around since the early ESX days and overtime we have learn how to play with Memory Reservations to constrain their maximum size and reduce storage footprint. This type of operation may not be as effective with server virtualization as it is with desktop virtualization.

The size of a .vswp file is equal to the memory size allocated to the VM, minus any assigned memory reservation. As an example, assume a virtual desktop with Windows 7 with2GB RAM, and 1GB memory reservation. In this case the .vswp file is 1GB.

As an example, in a deployment with 2,000 virtual desktops with 2GB RAM and 50% memory reservation the administrator would be able to save 1TB of storage footprint (2,000 x (2GB x 0.5) = 1TB).

The new *.VSWP file

ESxi 5.0 implements a second .vswp file for every virtual machine created either with hardware version 7 or 8. This second .vswp file is dedicated to memory overhead and will be used when the host is under resource constraint. When the virtual machine is created the memory overhead is defined, however the VM and the VMkernel will not use the whole reserved memory until required.

The total memory overhead is defined by the following factors:

• Number of virtual CPU
• Amount of RAM
• Amount of VRAM (defined by Number of Displays, Screen Resolution and Color Depth)
• 3D Support

Memory overhead is not something new and most VMware administrators were used to calculate overhead based on vCPU, RAM and VRAM. However, with the introduction of a Video memory Calculator, vSphere Client 5.0 provides an easy way to define the amount of VRAM required for a given video configuration.