es性能测试

用官方rally测试，发现一个奇怪的现象，配置了参数之后索引速度反而变慢了，任何参数都不配置速度比这个配置还要快点，求大神解惑
 
        "index.number_of_replicas": 0,
        "index.number_of_shards": 5,
        "index.translog.durability": "async",
        "index.translog.sync_interval": "10s",
        "index.refresh_interval": "120s",
        "index.translog.flush_threshold_size": "4g"