The Impact of Low-Entropy on Chunking Techniques for Data Deduplication
Mu'men Al Jarah, Sreeharsha Udayashankar, Abdelrahman Baba, Samer Al-Kiswany · 2024
While numerous Content-Defined Chunking (CDC) algorithms exist for data deduplication, their relative performance has not been analyzed in the presence of low-entropy induced byte-shifting. This paper explores and evaluates hash-based and hashless CDC algorithms in the presence of low-entropy data regions, using synthetic datasets. Our evaluation shows that modern CDC algorithms are poor at handling low-entropy blocks when the block sizes are small and that their low-entropy detection ability depends upon the expected average chunk size. Contrary to previous studies focusing on conventional byte-shifting, hash-based algorithms achieve poor space savings compared to their hashless counterparts when low-entropy induced byte-shifting is involved. This can be explained by the greater variability in chunk sizes and the higher percentage of artificial boundaries they exhibit in the presence of these regions. All of these factors together highlight the need for specialized CDC algorithms to detect and eliminate low-entropy data blocks during the deduplication process.