vSphere Consolidation Ratio Point -- vSwitch Ports

With vSphere and VI3, VMware virtualization environments can hit some very lofty consolidation ratios. Consolidation ratios of 30, 40 or 50 or more VMs per host are not at all out of reach today with host RAM of 128 GB or more and über quick processors. Guest operating system inventory makes a big difference as well. Consolidation ratios are aided by similar guest operating systems that will take advantage of the transparent page sharing technology and as-needed RAM provisioning to the guests.

When all of the stars are in alignment, you can find yourself with these high ratios. Both vSphere and VI3 have a default configuration that you may discover the hard way. The default number of ports for a vSwith on the host is 56 ports. You can easily increase this as part of your host build process to higher numbers such as 120, 248 or more. This is configured in the properties of the vSwitch (see Fig. 1).

Figure 1. vSphere Client shows the configured number of ports for a vSwitch. (Click image to view larger version.)

There will not be an obvious indicator that a host has a full vSwitch, other than VMotion tasks failing when another host goes into maintenance mode. Changing the number of ports does require a reboot (not sure why) for the vSwitch to be reconfigured.

I configure vSwitch port inventories at 120. This is a number that I really don't foresee occurring for the workloads that I have virtualized. VDI implementations or other situations may see a higher number of guests per host. Do you configure your vSwitch away from the default? Share your comments below.

Posted by Rick Vanover on 08/03/2009 at 12:47 PM