  DNA storage is a promising archival data storage solution to today's big data
problem. A DNA storage system encodes and stores digital data with synthetic
DNA sequences and decodes DNA sequences back to digital data via sequencing.
For efficient target data retrieving, existing Polymerase Chain Reaction (PCR)
based DNA storage systems apply primers as specific identifiers to tag
different sets of DNA strands. However, if a primer has collisions with any
payload in the same DNA tube, the primer cannot safely serve as an identifier
and must be disabled in this tube. In a DNA storage system with multiple DNA
tubes, the primer-payload collisions can spread over all DNA tubes, repeatedly
disable many primers, and cause a significant overall capacity reduction. This
paper proposes using a collision-aware data allocation scheme to allocate data
with different collisions into different tubes so that a primer banned in a
tube because of primer-payload collision can be reused in other tubes. This
allocation helps increase the number of usable primers over all tubes thus
enhancing the overall storage capacity. The executing time of our scheme is
$O(n^2)$ to the number of digital data chunks. The scheme serves as a
pre-processing method for any DNA storage system. The evaluation of the
state-of-the-art encoding scheme shows that the scheme can increase 20%-25%
overall storage capacity.
