Understanding Disk Alignment
The graphic above shows that SAN’s, VMFS, and NTFS virtual disks all have different block sizes. Aligning all these layers to start their disk units at the same place can make disk operations more efficient and keep the physical disks from working harder than necessary. For example, if these are not aligned, a call to read a single NTFS block may require the SAN to read three blocks as shown below:
The greatest efficiency is achieved when these layers are aligned so that the desired NTFS block requires only one SAN block to be read:
When VMFS volumes are created by the vSphere client, they are aligned on a 64K boundary. Check your SAN vendor’s documentation but in most cases the default 64K boundary will work.