My main array only holds larger static files.  I will be installing a new drive soon, as the array is getting full, and want to fill all the old drives to 90%, then not write to them anymore.  Only one share is stored on the main array and it uses high water allocation.  It didn't quite perfectly fill the drives as I was hoping, I assume I can use the exclude disks functionality to manually copy some files to the disk. I do have a cache drive however for example one drive has 617 GB free.  If I were to exclude all other disks from the share, copy 17 GB of data to the array, then start the mover, would this work as I hope? If so, then I assume I could do this for all the other disks then exclude all 90% disks from the share forcing writing to the new drive?  I want to confirm that excluding a disk from a share will not effect the data already on that disk.

Nevermind, I have managed to confirm that that will work as intended by changing the wording of my search.  I'll leave this up in case someone else wonders them same.

User Share settings only affect where new files are written. Nothing changes existing files, and in fact, those excluded disks are still part of the User Share for reading (unless the disks are excluded from ALL user shares in Global Share Settings).

 

You might also consider the Allocation Method: Fill Up for your purposes. Be sure to set a Minimum Free to avoid overfilling a disk. Unraid has no way to know how large a file will become when it chooses a disk to write the file. If a disk has less than Minimum Free, it will choose another disk. If a disk has more than Minimum Free remaining, it can be chosen, and if there is not actually enough space for a file the write will fail.