We present a "virtual node" simple graph representation for full-2 code(corresponds to complete graph)

this rep resentation simplifies the double erasure correcting data layout judgment theorem

the optimal redundancy data layo ut theorem and the construction of B-CODE.We also present a data layout construction method based on P1F of complete bipartite graph(corre sponds to 2d parity code)

this method can produce highly extensible double erasure correcting data layouts(BG-HEDP).Compared with other data layouts

such as B-CODE

BG-HEDP also has optimal update penalty

high reliability and low encoding/decoding complexity

its redundancy is very close to optimal value

while it is superior in extensibility to others.