Meta-Block: Exploiting Cross-Layer and Direct Storage Access for Decentralized Blockchain Storage Systems

Decentralized storage systems such as blockchain storage applications adopt the distributed storage technology and use distributed storage nodes to store the persistent data. For each off-chain storage node, key-value (KV) stores are normally used to manage data. As the most common data structure for KV store, Log Structured Merge Tree (LSM-Tree) eliminates random write operations and keeps acceptable read performance. Although LSM-Tree-based decentralized storage system can provide a secure and reliable storage platform, the unique feature of blockchain applications is not fully exploited. In blockchain storage applications, the generation of keys for KV stores is based on the encrypted data, and the key determines the allocation of data. Since the granularity for a read/write request at the level of blockchain storage platform is much smaller than that at the level of LSM-Tree or flash memory, a physical block in a solid-state drive (SSD) could be filled with data from different system users. This mixture of workloads will lead to the inefficient usage of physical spaces in the SSD and cause extra compaction operations for LSM-Tree. This paper presents Meta-Block , a cross-layer and efficient storage management strategy for decentralized blockchain storage applications. Meta-Block utilizes rich functionalities provided by the system infrastructure of open-channel SSD to provide direct storage accesses for the off-chain storage node. The objective is to capture the features of blockchain storage applications and reduce unnecessary read and write operations across different storage layers. As a cross-layer design, Meta-Block redesigns the organization of LSM-Tree, which can effectively reduce the write amplification. We also design a data prefetching strategy to speed up the indexing and enable direct storage access. We demonstrate the viability of the proposed technique using a set of extensive experiments. Experimental results show that Meta-Block can effectively reduce the write amplification and extend the lifetime of SSDs in comparison with representative schemes.