Performance impacts can be caused by the misalignment of the filesystem partitions. VMFS, like other filesystems, can suffer a penalty when the partition is not properly aligned. An unaligned guest operating system partition can result in the I/O crossing a boundary, causing additional I/O. This can negatively affect throughput and latency.

Use vCenter Server to create VMFS partitions; this issue is avoided because it will automatically align the partitions along the boundaries. However, if your storage vendor does not give you a specific recommendation, make sure to use a starting block that is a multiple of 8 KB. The esxtop utility can be used to monitor storage I/O impact.

The guest operating system data filesystem boundaries within the virtual machines must also be aligned once the VMFS partitions are aligned. It is not necessarily recommended to align the boot disk for a virtual machine; the data disks are the focus of alignment. This issue does not affect many of the newer...