When you use the hardware acceleration functionality, certain considerations apply.
Several reasons might cause a hardware-accelerated operation to fail.
For any primitive that the array does not implement, the array returns an error. The error triggers the ESXi host to attempt the operation using its native methods.
The VMFS data mover does not leverage hardware offloads and instead uses software data movement when one of the following occurs:
The source and destination VMFS datastores have different block sizes.
The source file type is RDM and the destination file type is non-RDM (regular file).
The source VMDK type is eagerzeroedthick and the destination VMDK type is thin.
The source or destination VMDK is in sparse or hosted format.
The source virtual machine has a snapshot.
The logical address and transfer length in the requested operation are not aligned to the minimum alignment required by the storage device. All datastores created with the vSphere Web Client are aligned automatically.
The VMFS has multiple LUNs or extents, and they are on different arrays.
Hardware cloning between arrays, even within the same VMFS datastore, does not work.