rocksDB
https://github.com/facebook/rocksdb/wiki/RocksDB-Basics
rocksdb 壓縮 知識
https://rocksdb.org/blog/2016/01/29/compaction_pri.html
https://github.com/facebook/rocksdb/wiki/Compaction
raft
https://ramcloud.stanford.edu/~ongaro/userstudy/raft.pdf
tidb
https://pingcap.com/blog/2017-09-15-rocksdbintikv/