notes: Check VAAI status with VCLI and VAAI hardware offload cannot be used when..

Thread Post in forums the by mcowger  <http://communities.vmware.com/message/2134534#2134534>

He was responding to a question on vaai appearing to not work,

If you see the vaai plug in name after running this command

esxcli storage core device vaai status get

 for example:   VAAI Plugin Name: VMW_VAAIP_CX

"Then VAAI is being recognized as available and being used when relevant.  Its definitly working.

Don't forget that VAAI acceleration is not used in all cases (especially clone operations):

VAAI hardware offload cannot be used when:

• The source and destination VMFS volumes have different block sizes <-- common issue
• 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 <-- also common
• The source or destination VMDK is any sort of sparse or hosted format
• Cloning a Virtual Machine that has snapshots (or doing a View replica or recompose), since this process involves consolidating the snapshots into the virtual disks of the target Virtual Machine.
• The logical address and/or transfer length in the requested operation are not aligned to the minimum alignment required by the storage device (all datastores created with the vSphere Client are aligned automatically)
• The VMFS datastore has multiple LUNs/extents spread across different arrays

Lastly, even with VAAI enabled and in use, we'd still expect the # of commands issued against the LUn to increase, because the VAAI commands still have to be sent.  We'd expect the actual THROUGHPUT against the LUN to be low, however."

Pasted from <http://communities.vmware.com/message/2134534#2134534>