vDCA550-Objective 1.2-3-Administer hardware acceleration for VAAI

VAAI enables the ESXi host to offload certain storage operations to the storage array, where they can be performed faster and consume less CPU and memory resources on the host. 

The three main built-in capabilities for VAAI.

  • Full copy
  • block zeroing
  • hardware-assisted locking (ATS)
  • Delete

You can check the VAAI capabilities from following esxcli command. SSH into the ESXi and run the below command.

#esxcli storage core device vaai status get


This command will tell you which capabilities offered by the VAAI and which one is currently supported. If all of these are supported by the Storage Array the vSphere Client will show the Hardware Acceleration as Supported and if none of them are supported by the SAN then the status will be Unsupported“.

Full Copy

The SCSI Extended Copy command is replaced by the VAAI XCOPY command, which enables the storage array to perform full copies of data completely within the storage array without having to communicate with the ESXi host during the reading and writing of data.

Block zeroing

When a new virtual disk is created with VMFS as an eager zeroed thick disk, the disk must be formatted and the blocks must be zeroed out before data can be written on them.

Hardware-assisted locking

VMFS is a shared cluster file system that requires file locking to ensure that only one host can write to the data at a time VAAI uses a single atomic test and set operation (ATS), ATS allows a VMFS datastore

To scale to more VMs per datastore and more ESXi hosts can attach to each LUN.


When a VM has been deleted. It will offload deleting process from ESXi and ask array to do this.

Things to Know:

  1. To take advantage of VAAI in vSphere. make sure your storage array can support VAAI
  2. Hardware acceleration for VAAI is supported for both SAN and NAS storage devices
  3. In case of “Block device”, if the storage device supports T10 SCSI commands, then by default the ESXi host can use VAAI. There is no need for any kind of configuration at vSphere end.
  4. In case of “NAS Device”. Hardware Accelerations not setup and enabled by default. you can implement NFS VAAI hardware acceleration by adding a vendor-specific NAS plug-in to the ESXi
  5. When VAAI is implemented on NAS device than you can provision “Thick disk” on NFS Storage

NOTE: If your storage does not support hardware acceleration then you have option to disable it from ESXi as well. To disable VAAI from ESXi. Use your vSphere Client and change the value of following advance settings into “0” from “1”

  1. HardwareAcceleratedMove
  2. HardwareAcceleratedInit
  3. HardwareAcceleratedLocking


Disable VAAI in ESXi

First check the hardware acceleration is enable in your datastore or not. You can find it from both vSphere Clients.

From Web client

Go to your ESXi hosts-> Manage -> Storage-> Storage devices-> Check “hardware Acceleration Tab” of your storage device.


From Classic client 

Go to your ESXi hosts->Configuration-> Storage-> Datastore-> Check “hardware Acceleration Colum” of your storage device


The three possible values for Hardware Acceleration

  • Unknown (The initial value is Unknown)
  • Supported (Unknown status changes to Supported after the host successfully performs the offload operation)
  • Not Supported (if the offload operation fails, the status changes to Not Supported)

Disable Hardware Acceleration on ESXi.

From Webclient -> select your ESXi host-> Manage-> Settings-> Advance System Settings -> Search “HardwareAccelerated” to filter the hardware Accelerated Settings.

Click on each of three settings -> choose “Pen Sign” to “Edit” its value from “1” to “0”.


Install NAS VAAI plugin in ESXi

Download the the NAS plugin from storage vender site. It will be available in “VIB” format.after downloading, move this plugin into the ESXi hosts where you want to install it.

# esxcli software vib install -d “path of the plugin”

Restart the ESXi host.

When your host is back.  To check the status of VAAI.

From GUI:

If install successfully-> From Classic Client ->Storage view. Make sure “hardware Acceleration” is showing as “ supported”.


From CLI:

Run the following ESXCLI command and check the status against your device.

#esxcli storage core device vaai status get

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