How do I know whether VAAI-block zero is actually being used?

Hmmm....interesting. I am looking at it to see what I can get back to you

Hi DLB,

I recommend you to read this document. http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h8115-vmware-vstorage-vmax-wp.pdf?mtcs=ZXZlbnRUeXBlPUttQ2xpY2tTZWFyY2hSZXN1bHRzRXZlbnQsZG9jdW1lbnRJZD0wOTAxNDA2NjgwNWQwMWY0LGRhdGFTb3VyY2U9RENUTV9lbl9VU18w

On page 30, Figure 16 shows the time difference of Block Zeroing different sizes of  devices. You can see, even with the VAAI on, Allocating 200GB virtual disks takes 6 or 7x time than allocating 10GB one. But allocating a 200G disk  with VAAI on is  18 times faster than without VAAI.

So my conclusion is it's expected result to see It's taking about 22 minutes to format 500 gb and maybe 30 seconds to do 5 gb with VAAI on.

imho, VAAI only guarantees efficiency which of course should (more-often-than-not) translate into faster times to complete the associated task.  Yes, offloading the tasks from the hypervisor (and corresponding reduced load on the intermediate FC/Ethernet/FCoE Switches) to a compliant array intuitively almost always should speed it up and every documented comparison correctly validates this {software bugs aside}.  However, it is also relative in that it should ultimately be compared between hardware offload enabled and disabled in your environment.  Of course, there is relevance in comparing to what others are achieving, but they are almost always accompanied with before and after graphs.

Even though Chad is using a VNX in the following video, try the same esxtop/resxtop tests where you should find the impact on the hypervisor appropriately change depending on whether it is enabled or not.  Also, he navigates to the appropriate performance charts in vSphere to see the same.  Then using array based performance tools (Unisphere Analyzer in the video), you'll see the resources accommodate on the back-end with a corresponding increase/decrease.

http://www.youtube.com/watch?v=1sUS-LcEtBY

Even though he is demonstrating the Hardware Accelerated Full Copy primitive, you can simply swap the option he is changing with: DataMover.HardwareAcceleratedInit instead which corresponds to the Write Same (zero) you are inquiring about.

There are also specific entries in the vmkernel logs you can parse for to also confirm that the hardware offload is, in fact, being used. Or similiarly whether or not it is reverting back to non accelerated mode with an otherwise VAAI compliant environment.  For instance, in the case of the Clone Blocks/Full Copy/XCOPY, there are several things that would disqualify it such as performing a Storage vMotion between two datastores (on the same array of course) that have different block sizes (when dealing with VMFS 3). 

Finally, I would also reference the following VMware KB article:

vStorage APIs for Array Integration FAQ

http://kb.vmware.com/kb/1021976

Chris, I know VAAI is enabled on VMAX by default. Is there a way to disable it from storage side using SE/SMC/SymmWin? Or if there is any utility to monitor the VAAI status from storage side?

jingyi wrote: Chris, I know VAAI is enabled on VMAX by default. Is there a way to disable it from storage side using SE/SMC/SymmWin?

No, it is enabled/disabled using the Advanced Settings per host:

DataMover.HardwareAcceleratedMove
DataMover.HardwareAcceleratedInit
VMFS3.HardwareAcceleratedLocking

jingyi wrote: Or if there is any utility to monitor the VAAI status from storage side?

Yes, use the array performance tools (comparable to Unisphere Analyzer for VNX) to monitor as demonstrated in the video.