memsql_memsql olap_memsql 5(2)

已部署的汇聚器和叶子节点的数量决定了集群的存储容量和性能。典型的部署结构中，叶子节点和汇聚器的比例为5:1。在一个设计良好的集群中：

当集群需要比较高的连接能力的时候，汇聚器比叶子节点的比率要较高

当集群需要比较大的存储容量时，叶子节点比汇聚器的比率要比较高

你能够列出所有的汇聚器和叶子节点通过使用SHOW AGGREGATORS和SHOW LEES命令

memsql> SHOW AGGREGATORS;
+---------------+-------+--------+--------------------+---------------------------+-------------------+
| Host          | Port  | State  | Opened_Connections | Average_Roundtrip_Latency | Master_Aggregator |
+---------------+-------+--------+--------------------+---------------------------+-------------------+
| 127.0.0.1     |  3306 | online |                  0 |                      NULL |                 1 |
| 192.168.1.116 |  3306 | online |                  1 |                     0.200 |                 0 |
+---------------+-------+--------+--------------------+---------------------------+-------------------+
2 rows in set (0.00 sec)

memsql> SHOW LEES;
+---------------+-------+--------------------+---------------+-----------+--------+--------------------+---------------------------+
| Host          | Port  | Availability_Group | Pair_Host     | Pair_Port | State  | Opened_Connections | Average_Roundtrip_Latency |
+---------------+-------+--------------------+---------------+-----------+--------+--------------------+---------------------------+
| 192.168.1.110 |  3306 |                  1 | 192.168.1.112 |      3306 | online |                  5 |                     0.299 |
| 192.168.1.111 |  3306 |                  1 | 192.168.1.113 |      3306 | online |                  5 |                     0.293 |
| 192.168.1.112 |  3306 |                  2 | 192.168.1.110 |      3306 | online |                  1 |                     0.271 |
| 192.168.1.113 |  3306 |                  2 | 192.168.1.111 |      3306 | online |                  1 |                     0.264 |
+---------------+-------+--------------------+---------------+-----------+--------+--------------------+---------------------------+

除了复制时的数据传输，所有MemSQL节点间的通信都是通过SQL命令实现的。比如说，集群心跳是通过select 1查询实现的而非特殊的接口。

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