Your customer want you to add a new volume in one of the VM Windows server but can not affort down time? No worry, you can do that easily with ESX.

Below is step by step guide with screen captured from the VM (my test machine is running on Windows 2003 Enterprise):

Tip: It is best to do a snapshot before you start this task, incase anything goes wrong.

This is my test VM machine. It is having one disk at beginning.

1) This is my test VM machine. It is having one disk at beginning.

This is my test VM machine. It is having one disk at beginning.

2) I am going to add the second disk with 2GB space.

This is my test VM machine. It is having one disk at beginning.

3) Click on Action, then choose "Rescan Disks".

This is my test VM machine. It is having one disk at beginning.

4) Windows detected a new disk.

This is my test VM machine. It is having one disk at beginning.

5) You need to initialize the disk before you can use it.

This is my test VM machine. It is having one disk at beginning.

6) Format it and map it as E:"

Ok, our job done. Now you have a new volume on the Windows box.