Efficient transaction processing over large databases is a key requirement for many mission-critical applications. Though modern databases have achieved good performance through horizontal partitioning, their performance deteriorates when cross-partition distributed transactions have to be executed. This paper presents Solar, a distributed relational database system that has been successfully tested at a large commercial bank. The key features of Solar include: 1) a shared-everything architecture based on a two-layer log-structured merge-tree; 2) a new concurrency control algorithm that works with the log-structured storage, which ensures efficient and non-blocking transaction processing even when the storage layer is compacting data among nodes in the background; 3) fine-grained data access to effectively minimize and balance network communication within the cluster. According to our empirical evaluations on TPC-C, Smallbank and a real-world workload, Solar outperforms the existing shared-nothing systems by up to 50x when there are close to or more than 5% distributed transactions.