In the early days of VMware people had a lot of VMs that were converted from physical machines and this causes a nasty alignment issue between the VMDK blocks a

In the early days of VMware people had a lot of VMs that were converted from physical machines and this causes a nasty alignment issue between the VMDK blocks and the blocks on your storage array. The effect was to always add one block to every read operation, and in the worst case of reading one block would double the load on the storage array. On NetApp this could only be fixed when the VM wasn't running.