Drive Reserved Space Size (64KB units). When set,
the index into the 'Valid Value List' should
be passed in rather than the size itself.
This will trigger a format or unformat
operation (depending on the direction of the
change) is performed on the drive reserved
space. Note that it is an error to try and
change a the size of the reserved space
without unformatting first or to try and
unformat a drive that has been configured as
a LD member or as a spare/clone.