The device has already been claimed by vSAN, so it is now part of the vSAN ESA storage pool. It must be removed from vSAN through a controlled device-removal workflow before it can be repurposed for memory tiering. The correct method is to remove the device from vSAN using Full Data Migration. This evacuation mode migrates data from the device to other eligible devices or hosts so that objects remain protected and compliant where possible. After the device is safely removed from the vSAN storage pool, it can be configured for memory tiering. Physically removing or hot-removing the device is unsafe because vSAN may still have components on it. Booting without the device is also not a supported configuration workflow. Changing disk claiming behavior and rebooting does not safely remove existing components from the already claimed device. vSAN ESA uses a storage pool model, so claimed NVMe devices contribute capacity and performance; a device intended for another purpose must be explicitly evacuated and removed before reuse. Reference topics: vSAN ESA Storage Pools, Device Claiming, Remove Storage Pool Device, Full Data Migration, Memory Tiering.