A virtual machine's swap file is host-local (the swap file is stored in a specified datastore that is on the host). The swap file cannot be relocated and Storage DRS is disabled for the swap file disk.

A certain location is specified for a virtual machine's .vmx swap file. The swap file cannot be relocated and Storage DRS is disabled on the .vmx swap file disk.

The relocate or Storage vMotion operation is currently disabled for the virtual machine in vCenter Server (for example, because other vCenter Server operations are in progress on the virtual machine). Storage DRS is disabled until the relocate or Storage vMotion operation is re-enabled in vCenter Server.

The home disk of a virtual machine is protected by vSphere HA and relocating it will cause loss of vSphere HA protection.

The disk is a CD-ROM/ISO file.

If the disk is an independent disk, Storage DRS is disabled, except in the case of relocation or clone placement.

If the virtual machine has system files on a separate datastore from the home datastore (legacy), Storage DRS is disabled on the home disk. If you use Storage vMotion to manually migrate the home disk, the system files on different datastores will be all be located on the target datastore and Storage DRS will be enabled on the home disk.

If the virtual machine has a disk whose base/redo files are spread across separate datastores (legacy), Storage DRS for the disk is disabled. If you use Storage vMotion to manually migrate the disk, the files on different datastores will be all be located on the target datastore and Storage DRS will be enabled on the disk.

The virtual machine has hidden disks (such as disks in previous snapshots, not in the current snapshot). This situation causes Storage DRS to be disabled on the virtual machine.

The virtual machine is a template.

The virtual machine is vSphere Fault Tolerance-enabled.

The virtual machine is sharing files between its disks.

The virtual machine is being Storage DRS-placed with manually specified datastores.