The document discusses fragmentation issues that arise from data deduplication in backup storage systems. It proposes three algorithms - History-Aware Rewriting algorithm (HAR), Cache-Aware Filter (CAF), and Container-Marker Algorithm (CMA) - to address these issues. Experimental results on real-world datasets show that HAR can significantly improve restore performance by 2.84-175.36 times while only rewriting 0.5-2.03% of data.