Overwrite oldest files automatically

That is not the way it works in fact most times I always see a recommended 5-10% should be empty at all times.

 

The operating system itself has the ability if you copy file to same location as old it prompts you to overwrite. What you do not understand is full hard drive slows down machine.

 

Ok I see in that case I use program called DropSync which automatically will delete files on the destination drive/directory that are not present on the source so will do exactly what you need. This is just a front end for the built in rsync so you can use that instead if you wanted from the command line to achieve the same result.

 

What would you want to happen if the old file is smaller than the newer file, and there's not enough space for the "automatic" replacement?
Easier would be to use a smart folder, which keeps only some number of files. Adding a file would then delete the oldest file.
However, that still would not allow for total space on the hard drive, would it?

The better idea is to NOT have the hard drive full in the first place.
If the hard drive is jammed full, then you need more space (storage is cheap), not some work-around to "delete the oldest file"

 

You would not do the whole drive just the directory(ies) you want to have identical contents.