Now that you understand the disk alignment it’s time to check your environment and see how big the issue on your environment is.
Vizioncore has a good tool for the job vOptimizer !!
You can download a free tool that will scan your environment and tell you which guest is not 64k aligned. It’s called vOptimizer Waster Finder and you can download it from here.
Here’s also a good presentation about the product.
It also brings some cool reports. Here's an exaample of the disk alingment report.

You will probably notice a product called vOptimizer Pro, ok, that’s the paid version; it does a lot of other cool tricks, like resizing the disks and make the correct alignment of the disk.
But how to make a disk aligned is a subject for another topic….