When ESXi creates a VMfs filesystem with storage that supports VAAI, ATS file locking will be used. If VAAI support is sisabled in the storage, ATS file locking will no longer work. As a result of this ESXi will be able see the LUN, but not the datastore.

With most storage VAAI cannot be enabled and disabled, so this will not be a problem. But with newer Promise Ex30 and Vess 2000 series firmware, there is a softswitch to enable or disable VAAI.

When updating from older firmware on the Ex30 and Vess 2000 series to the latest firmware, because there is no previous VAAI setting to inherit, the VAAI softswitch will be in the disabled position, and any ESXi server that the storage is connected to will no longer be able to see the datastore.

To see the datastore VAAIsupport must be re-enabled in the storage..

In the Vess 2000 series, VAAI can be enabled from WebPAM PROe. It is a controller setting and a reboot will be required for the setting to take effect.

It’s in System > Component List > Controller 1 > Settings.

The Ex30 does not have a GUI setting and VAAIsupport must be enabled or disabled in the CLI. The CLI command given works in both the Ex30 and the Vess 2000.

Enabling VAAI:

- Establish a telnet, ssh or serial connection to the VTrak or Vess 2000

On a command prompt type the following command using the IP of your subsystem management port. You will need the administrator password to login.

telnet example: telnet 2300
ssh example:   ssh administrator@

The CLI command to enable VAAI

administrator@cli> ctrl -a mod -s "VAAIsupport=enable"

Note: While the GUI gives a warning that a reboot is required, the CLI command does not. The VAAIsupport setting will take effect only after next subsystem reboot

A rescan in ESXi will show if any new LUNs are visible or if any existing LUNs are no longer visible, but it will not necessarily pick up any other changes to the storage, such as whether the VAAI (hardware acceleration) status has changed. As a result the ESXi server will also need to be rebooted.

ESXi will also work without VAAI. If a datastore is created with VAAI disabled, ATS file locking will not be used and the datastore will be visible whether VAAI is enabled or disabled. But if a datastore is created with VAAI enabled, ESXi will only be able to see the datastore when VAAI is enabled.