This statement doesn't make much sense to me. Is there a theoretical limit to the length of DNA, or do you mean that human DNA is ~100MB?
The human genome is about 6.4 billion base pairs, where each base pair is represented by the letters: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G), i.e. 2-bits. 6,4 billion is then 6.4E9*2 = 1.28E10 bits = 1.28E10/8 bytes = 1600 MB. Or 800 MB if you count the bases as pairs of two.
Polychaos dubium's DNA is over 200 times as long as human DNA[0].