I have been asked, recently, about “how do I make my VMs run better?” This is a loading question, if I have ever heard one. There are a lot of things that you can do to increase the performance of the Virtual Machines on an ESX host.
In a SAN environment, one things that you can do to increase the performance of your VMs, is to align the partition. 64KB Track Alignment for both the physical host and the VM partitions yield I/O performance improvements, such as, reduced latency and increased throughput.
An unaligned partition results in a track crossing and an additional I/O, incurring a penalty on latency and throughput. The additional I/O (especially if small) can impact system resources significantly on some host types. An aligned partitions ensures that the single I/O is serviced by a single device, eliminating the additional I/O and resulting in overall performance improvement.
You need to align, not only the SAN LUN, but the VMFS Partition and all guests on the ESX server. Here is a link to the VMWare document that explains the “How To”. Link