This article provides answers to frequently asked questions about vStorage APIs for Array Integration (VAAI).

• ESXi/ESX 4.1 or later
• Standard, Enterprise, Enterprise Plus or Remote Office Branch Office licensing for ESXi/ESX hosts
• Storage arrays that support VAAI storage-based hardware acceleration
  
  Notes:
  
  • ESXi/ESX 4.1 does not support hardware acceleration with NAS storage devices.
  • Support for NAS storage devices was introduced in ESXi 5.x.

• In VMware HCL version 2, there are options under the Features Category and Features fields where arrays can be searched against to verify if they are VAAI-certified.

• Atomic Test & Set (ATS), which is used during creation and locking of files on the VMFS volume
• Clone Blocks/Full Copy/XCOPY, which is used to copy or migrate data within the same physical array
• Zero Blocks/Write Same, which is used to zero-out disk regions
• Thin Provisioning in ESXi 5.x and later hosts, which allows the ESXi host to tell the array when the space previously occupied by a virtual machine (whether it is deleted or migrated to another datastore) can be reclaimed on thin provisioned LUNs.
• Block Delete in ESXi 5.x and later hosts, which allows for space to be reclaimed using the SCSI UNMAP feature. For more information on Block Delete/SCSI UNMAP, see Using vmkfstools to reclaim VMFS deleted blocks on thin-provisioned LUNs (2014849).

• Full File Clone – Like the Full Copy VAAI primitive provided for block arrays, this Full File Clone primitive enables virtual disks to be cloned by the NAS device.
• Native Snapshot Support – Allows creation of virtual machine snapshots to be offloaded to the array.
• Extended Statistics – Enables visibility to space usage on NAS datastores and is useful for Thin Provisioning.
• Reserve Space – Enables creation of thick virtual disk files on NAS.
  
  Note: Previously, the only supported VMDK type that could be created on NAS was thin.

1. In the vSphere Client inventory panel, click the host.
2. Click the Configuration tab, then click Advanced Settings under Software.
3. Check that these options are set to 1 (enabled):
   
   DataMover.HardwareAcceleratedMove
   DataMover.HardwareAcceleratedInit
   VMFS3.HardwareAcceleratedLocking
   
   Note: These options are enabled by default.

What happens if I have VAAI enabled on the host but some of my disk arrays do not support it?

When storage devices do not support or provide only partial support for the host operations, the host reverts to its native methods to perform the unsupported operations.

Are there any caveats that I should be aware of in ESXi 5.x?

Use of the Atomic Test-and-Set (ATS) primitive depends on the type of filesystem:

• If a new VMFS-5 is created on a non-ATS storage device, SCSI-2 reservations will be used.
• When creating a multi-extent datastore where ATS is used, the vCenter Server will filter out non-ATS devices, so that only devices that support the ATS primitive can be used.

• The source and destination VMFS volumes 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 any kind of sparse or hosted format
• Cloning a virtual machine that has snapshots because 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 is 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

• When using enhanced vMotion (move both VM and datastore simultaneously), the source and destination hosts must both see the source and destination datastores, or the file transfer defaults to NFC over the the management network, instead of VAAI.
• Hardware cloning between arrays (even if within the same VMFS datastore) does not work.
• For more information on supportability with Horizon View, see View Composer API for Array Integration (VCAI) support in VMware Horizon View (2061611).
  

What do I need to know about the Hardware Acceleration Support Status?

If you go to Host > Configuration > Storage, you can see the Hardware Acceleration Status in the panel on the right side.

For each storage device and datastore, the vSphere Client displays the hardware acceleration support status in the Hardware Acceleration column of the Devices view and the Datastores view.

The status values are Unknown, Supported, and Not Supported. The initial value is Unknown. The status changes to Supported after the host successfully performs the offload basic operations. If the offload operation fails, the status changes to Not Supported.

To determine if your storage device supports VAAI, test the Full Copy VAAI primitive:

1. Using the vSphere Client, browse the datastore and locate a virtual disk (VMDK) of at least 4 MB that is not in use.
2. Copy the virtual disk to a new file.
3. Check the Hardware Acceleration status to verify that it changes from Unknown to either Supported or Not Supported.

• On ESXi 5.x
  
  To check the VAAI status, run this command:
  
  # esxcli storage core device vaai status get
  
  You see output similar to:
  
  mpx.vmhba1:C0:T1:L0
  VAAI Plugin Name:
  ATS Status: unsupported
  Clone Status: unsupported
  Zero Status: unsupported
  Delete Status: unsupported
  
  mpx.vmhba1:C0:T0:L0
  VAAI Plugin Name:
  ATS Status: unsupported
  Clone Status: unsupported
  Zero Status: unsupported
  Delete Status: unsupported
  
  
• On ESXi/ESX 4.x
  
  To check the VAAI status, run this command:
  
  # esxcfg-scsidevs -l | egrep "Display Name:|VAAI Status:"
  
  You see output similar to:
  
  Display Name: Local VMware Disk (mpx.vmhba2:C0:T0:L0)
  VAAI Status: unsupported
  Display Name: Local USB CD-ROM (mpx.vmhba32:C0:T0:L0)
  VAAI Status: unknown
  Display Name: Local TEAC CD-ROM (mpx.vmhba3:C0:T0:L0)
  VAAI Status: unknown
  Display Name: DGC Fibre Channel Disk (naa.6006016030801c00f8506073d0d7de11)
  VAAI Status: unknown
  Display Name: DGC Fibre Channel Disk (naa.6006016030801c00f9506073d0d7de11)
  VAAI Status: unknown

VAAI For NAS Storage

In ESXi 5.x, NAS Hardware Acceleration was introduced with support for these primitives:

· Full File Clone – Like the Full Copy VAAI primitive provided for block arrays, this Full File Clone primitive enables virtual disks to be cloned by the NAS device.

· Native Snapshot Support – Allows creation of virtual machine snapshots to be offloaded to the array.

· Extended Statistics – Enables visibility to space usage on NAS datastores and is useful for Thin Provisioning.

· Reserve Space – Enables creation of thick virtual disk files on NAS.

With NAS storage devices, the hardware acceleration integration is implemented through vendor-specific NAS plug-ins. These plug-ins are typically created by vendors and are distributed as VIB packages through a website. No claim rules are required for the NAS plug-ins to function.

The host acceptance level must be the same or less restrictive than the acceptance level of any VIB you want to add to the host. The value can be one of the following:

· VMwareCertified

· VMwareAccepted

· PartnerSupported

· CommunitySupported

# esxcli software vib install –-viburl=URL

The URL specifies the URL to the VIB package to install. http:, https:, ftp:, and file: are supported.

Verify Hardware Acceleration Status for NAS

You can verify the NAS hardware acceleration status using the following command:

# esxcli storage nfs list

Disabling VAAI when using NAS storage

To disable NAS VAAI functionality the plugin must be removed using the below commands.

Note: The advanced configuration options for Block VAAI mentioned above (DataMover.HardwareAcceleratedMove, DataMover.HardwareAcceleratedInit, VMFS3.HardwareAcceleratedLocking) do not affect NAS VAAI functionality

• vSphere 5.5 Storage Guide
• vSphere 5.1 Storage Guide
• vSphere 5.0 Storage Guide
• vSphere 4.1 SAN Configuration Guide