I was messing around with some code to export and validate machine disks.
There are 787 unique machine disks (0.217). I wanted to see if I can work from a disk set that included no duplicates.
It would appear that MAME requires some disks to be duplicated.
Here is an example.
Children: "area51t" and "area51ta"
Both these children use the disk "area51t" "d2865cc7b1bb08a4393a72013a90e18d8a8f9860".
I can run "area51t" just fine.
If I try to run "area51ta" I get "Required files are missing".
If I copy "area51t/area51t.chd" to "area51ta/area51t.chd" it works.
So this means I need to duplicate disk files in the set.
Is this something that could be fixed in the driver XML? Maybe change area51ta's machine.romof from "area51" to "area51ta" and set disk.merge to "area51t"?
I can see a few of these, that was just the first example I hit.