Doh… too late, I done it guv
And again… what I’m thinking is that people (me me me) will have different disks on a machine, with different performance (e.g. I will have Odroids with 64G eMMC RAM and HDD). Others might have an SSD and an HDD.
One might want to have an eMMC vault and an HDD vault etc. And to have one being filled first (e.g. because its a faster disk and will get better farming performance, or because it has lots of free space etc.).
Later I can imagine machine resource allocations needing to be changed - your disk migration/replacement - also adding another disk, meaning it would be useful to be able to move, expand, shrink, add remove, vaults etc. The priorities part helps a user manage their resources both to maximise farming (which benefits the network) and as things change over time.
I know it sounds a bit like making the system handle system functions, but its really more about optimising farming resources on a particular machine, and enabling these to be adjusted later.