I'm trying to understand how a cache drive would work for data where you are regularly acessing and modifying the file.  Take for example an Excel file that is stored on the unraid server and accessed via SMB on a Windows PC.  If I were to use a cache drive and open the excel document would it be copied from my array to the cache drive when I open it and then leave it there until the end of the day when mover moves it back?  What if the file is still open on the Windows PC when mover wants to run?

If a file already exists it is opened ‘in situ’ wherever it already is (cache or array) at the moment.  The cache drive would come into play for new files.