There are generally two categories of RAID6 codes in their code structures

horizontal codes and vertical codes.Horizontal codes are very easy to be extended to an arbitrary length

while the lengths of vertical codes are usually restricted.We propose a novel and efficient code shortening algorithm for vertical codes

by which the length of a vertical code can be extended to an arbitrary given one.The shortening algorithm maintains the MDS (Maximum Distance Separable) property of the vertical codes.In the context of our shortening algorithm for vertical codes

we conduct an performance analysis on the representative vertical and horizontal RAID6 codes at all code lengths

and reveal the impacts of the code shortening algorithms on the performance of the RAID6 codes in various performance metrics.