If ESXi does not automatically 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 HDD disks as flash disks could deteriorate the performance of datastores and services that use them. Mark disks as flash disks only if you are certain that those disks are flash disks.


Verify that the device is not in use.


  1. Browse to the host in the vSphere Web Client object navigator.
  2. Click the Manage tab, and click Storage.
  3. Click Storage Devices.
  4. From the list of storage devices, select one or several HDD devices that need to be recognized as flash devices and click the Mark as Flash Disks 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.