示例：将 keyspace 大小增加到 5GB

扩展 etcd 磁盘性能

示例：调整主机上的磁盘优先级

---
services:
  etcd:
      data-dir: "/var/lib/rancher/etcd/data/"
      wal-dir: "/var/lib/rancher/etcd/wal/wal_dir"
    extra_binds:
      - "/var/lib/etcd/wal:/var/lib/rancher/etcd/wal"