Variant record memory storage question

[NiGHTS <nights@unku.us>]

Say I had a variant record like this:

type Which_One is (Is_Small, Is_Big);

type Variant_Record (Option : Which_One) is 
record
    case Option is
        when Is_Small =>
            Var_1 : Byte -- 1 byte
        when Is_Big =>
            Var_2 : Some_Large_Record -- 1000 bytes
    end case;
end record;

Will the record Variant_Record( Is_Small ) be stored as 1 byte? Or does it act almost like a C union allocating the memory for Variant_Record( Is_Big ) even though it will never morph at run-time?

I am trying to determine the most memory-efficient way to store a complex record and it seems Variant_Record can help me do this, but I am unsure if it will work the way I think it will.

Note I am using gcc. Thank you.