When cache has a file on it larger than available space on most of your drives, it will try and fail to write the file to several of the array drives in order until it finds one that will fit the file. This causes Mover to take much longer than is needed.
I feel it would be more efficient if Mover first got file properties of the file it was trying to move and then queried the different array drives to check free space before attempting to move the file.
Example:
Cache has a 100GB file on it and my 3 data drive array has 3 disks. Disk1 has 50GB free, 2 30GB free, 3 500GB free. Unraid will write 50GB to Disk1 and then write 30GB to 2 before finally writing the complete file to 3. It does delete the partial file when it is done on Disk1 and Disk2, but this is just a very slow process for large files that wastes a lot of time.
Preferred behavior: Write the file to 3 since the OS is already aware of free space and it's not very expensive to check file size before a move.