diskSize → An unsigned 64bit integer, indicating the intended home directory disk space in bytes to assign to the user. Depending on the selected storage type this might be implement differently: for luks this is the intended size of the file system and LUKS volume, while for the others this likely translates to classic file system quota settings.
diskSizeRelative → Similar to diskSize but takes a relative value, but specifies a fraction of the available disk space on the selected storage medium to assign to the user. This unsigned integer value is normalized to 2^32 = 100%.
https://github.com/poettering/systemd/blob/homed/d...