Unassigning flash devices
If you need a larger or smaller flash device on a host, you can stop using the currently initialized device and start using a different one. You need to unassign the current device before assigning and initializing the new device.
Before you begin 
You must disable caching and deallocate cache space on each affected virtual machine.
Note: If the host on which you are unassigning the flash device is a potential target for migration, you must deallocate cache space not only on its VMs, but on every VM for which it is a potential target.
Steps 
1.
From the Host Inventory page of the FAMC, click the wrench icon for the host on which you want to unassign the flash device and select Flash Device > Unassign.
The Unassign flash device dialog opens.
2.
Click Unassign.
Result 
The flash device is unassigned.
After you finish 
Assign a new flash device on the host, then reallocate cache space and enable caching on each affected virtual machine.
Parent Topic: Assigning and unassigning flash devices