Improve your vSphere client's performance

Are you tired of staring at this window?

vSphere Client taking ages to load a VM view

If you manage a vSphere environment with several hundreds of VMs you might notice a disturbing slowness in screen refreshes when you initially look at lists of lots of VMs, try to refresh such views or resort them by clicking on the attributes' columns.

We have been struggling with this for a long time (in fact, since we upgraded to vSphere 4) without ever finding out how to improve or resolve this.
Now I got the tip to look at VMware's KB1029665. It exactly describes this symptom and recommends tuning the Java Memory pool of the Tomcat installation that is used on the vCenter server.

And yes, it got better after implementing this! Don't expect miracles - the first load of the complete VM view will still be slow, but subsequent viewing, sorting and scrolling is faster than without his modification.
However, you need to be aware that this actually changes the memory footprint of the vCenter server. So you might want to review its RAM configuration. Easy, if you have it running as a VM ...

Using hardware-assisted virtualization in Windows Server 2003 32-bit virtual machines

This is the title of a VMware KB article (KB2001372) that was recently posted, and it includes very interesting information for anyone running virtualized Windows 2003 servers on vSphere (so, probably all of us).

ESX(i) is able to use different methods for virtualizing the CPU and associated MMU (memory management unit) instruction sets. You can configure that for a VM in its Advanced Options / CPU/MMU virtualization:

CPU/MMU virtualization settings

In the Binary Translation (BT) mode software emulation is used for both CPU and MMU instructions (the second choice in the picture). For a long time this was the only option, until the CPU vendors Intel and AMD started building virtualization functions into their processors.
Choosing the third option will enable these hardware functions for the CPU instruction set virtualization (if available), but will remain using software virtualization for MMU instructions.
The fourth option will enable hardware virtualization for both types of instructions if available.
It depends on the CPU generation whether none, only the first or both hardware virtualization options are available. Since quite a few years Intel's and AMD's processors support CPU as well as MMU virtualization.

The default in the above dialog is "Automatic". This means that ESX(i) will choose what it considers to be the best option for the type of operating system that you have selected for the VM.
With Windows 2003 this is the "Software" mode. The reason for this is that Windows 2003 with SP1 in fact performs better with software emulation than with hardware virtualization. However, this changed with code changes introduced by Microsoft with SP2. Windows 2003 with SP2 performs better with hardware virtualization in almost any case.
Today, most Windows 2003 servers should have been updated with SP2. So, to ensure best performance you should go and change the virtualization mode of these VMs to one of the hardware-assisted ones.

For more details see the KB-article mentioned above.