Towards High-performance Transactions via Hierarchical Blockchain Sharding

Blockchain sharding, a promising approach to improve system performance, divides the network into several small parallel working shards. However, the performance of existing sharded blockchain systems may degrade seriously due to the existence of cross-shard transactions. To overcome such drawbacks, we propose a blockchain system called HieraChain to process transactions with robust cross-shard transactions tolerance, based on a novel hierarchical sharding architecture. The upper-layer shards order the cross-shard transactions and the participants process them asynchronously to pipeline the transactions ordering. Furthermore, HieraChain proposes an optimized locality-aware protocol to trade off the local access patterns and the induced remote access events. Extensive experimental results demonstrate that HieraChain outperforms the state-of-the-art approaches significantly in the presence of cross-shard transactions, achieving up to 3× and 2× higher throughput than Saguaro and SharPer under general workload respectively. Moreover, our locality-aware approach further reduces transaction latency by 68 % and 51% compared to our basic approach and traditional baselines, respectively.