If ESXi does not recognize its devices as flash, mark them as flash devices.

ESXi does not recognize certain devices as flash when their vendors do not support automatic flash disk detection. The Drive Type column for the devices shows HDD as their type.
Caution: Marking the HDD devices as flash might deteriorate the performance of datastores and services that use them. Mark the devices only if you are certain that they are flash devices.


Verify that the device is not in use.


  1. In the vSphere Client, navigate to the ESXi host.
  2. Click the Configure tab.
  3. Under Storage, click Storage Devices.
  4. From the list of storage devices, select one or several HDD devices and click the Mark as Flash Disk (Mark as flash disk.) icon.
  5. Click Yes to save your changes.


The type of the devices changes to flash.

What to do next

If the flash device that you mark is shared among multiple hosts, make sure that you mark the device from all hosts that share the device.