By default, there are 3 user shares used by Dockers and VMs. These are appdata, domains, and system; appdata is the working storage for your dockers. domains is where your VMs are stored, and system is where docker and libvirt images are stored.
These shares are set as cache-prefer by default. So, they will be stored on cache if cache has space, and moved from array to cache when cache has space. You want these shares on cache so your Docker and VM performance will not be affected by the slower parity writes, and so your Dockers and VMs won't keep array disks spinning, since these files are typically in use.
But, mover can't move open files. So, to get these moved to cache, you have to disable Docker (Settings - Docker) and VM (Settings - VM Manager) services, then run mover.
After you get them all moved to cache you might consider setting all these shares to cache-only if you are sure you won't fill cache (Settings - Global Share Settings - Cache Settings - Min. free space).
You can see how much of each disk each user share is using at Shares - User Shares and doing Compute... for a share, or the Compute All button.