# Comprehensive Review of Storage Optimization Techniques in Blockchain Systems
## 4 Methods
### Data Deduplication  
Data Deduplication [89] is an advanced data reduction technology widely utilized in storage-sensitive environments. By identifying and eliminating redundant data within storage systems, deduplication processes data at different granularity levels, including file-level, block-level, and byte-level deduplication. For each set of redundant data, only a unique instance is preserved, with other instances referencing this copy via pointers \begin{table}
\begin{tabular}{c c c c} \hline \hline
**References** & **Implementation Strategies** & **Storage Efficiency** & **Usage Scenario** \\ \hline Qi [83] & Byzantine fault tolerance & High & Blockchain network with malicious nodes \\ Qu [84] & Gcblock,TFR encoding & High & System affected by physical distance \\ Qi [85] & Byzantine fault tolerance & High & Erasure coding byzantine nodes \\ Fan [86] & LEA algorithm & Midium & Blockchain System \\ Xiao [87] & ER-MRS & Midium & Blockchain System \\ Xu [88] & MTEC & High & IOT scenario \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Erasure coding to reduce storage redundancy. or references. This approach not only ensures data integrity and consistency but also maximizes storage space efficiency without compromising data access speed. Additionally, deduplication substantially reduces storage costs and enhances overall system performance, which makes it particularly advantageous in domains such as large databases, virtualized environments, and backup systems. By effectively managing and minimizing redundant data, deduplication plays a crucial role in supporting the efficient operation of modern data centers [90]. The deduplication process is depicted in Figure 12. In this illustration, file 4 is corrupted, files 2* and 8* represent modified versions of the original files 2 and 8, and A, B, and C are newly added files. Through the deduplication process, fingerprint data, delta files, and fingerprint files are generated. [PERSON] et al. [91] proposed a Blockchain-based Cloud Data Deduplication aimed at optimizing the utilization of blockchain storage resources. In this scheme, the data uploaded by users is first hashed to generate a unique hash value, which is then compared with existing hash values on the blockchain to detect any redundant data. If the system detects that the data already exists, it avoids storing a new data copy. Instead, it updates the metadata of the existing data entry to append the ownership and access rights of the new user to the current entry. This deduplication mechanism is implemented through smart contracts, which are responsible for autonomously executing the deduplication process and recording each step on the blockchain to ensure the uniqueness of stored data and to guarantee transparency and fairness throughout the process. Through this method, not only is data redundancy within blockchain storage significantly reduced, enhancing the efficiency of storage resource utilization, but it also ensures the fair distribution of benefits among all parties, providing an efficient and scalable solution for blockchain applications in large-scale data management. [PERSON] et al. [92] proposed a Blockchain-Based Secure Deduplication Scheme with Reliable Key Management (BDKM) to optimize cloud storage resource utilization by enhancing the data storage structure. This scheme employs file-level and block-level deduplication techniques, generating unique identifiers by hashing data blocks and comparing them with existing hash values in the storage system to detect and eliminate redundant data. During the deduplication process, if duplicate data are detected, the system avoids storing a new data copy and instead updates the metadata of the existing data entry to record the  
Figure 12: Deduplication process. new user's access rights, effectively reducing storage space consumption.