2019/1/21 星期一

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2.3.1. balancer
运行一个集群平衡工具。管理员可以通过按Ctrl+C键停止再平衡过程。
数据平衡的需求
HDFS数据不平衡的原因
1.某个DataNode机器内硬盘存储达到饱和值。
2.集群内新增、删除节点。
数据不平衡的影响
1.Map任务可能会被分配给没有存储数据的机器，结果是不能实现本地计算，最终会导致网络
带宽的消耗。
2.当一些数据节点数据完全满载时，新的数据块只会被存放在有空余数据的节点机器上，造成了并行读取的可能性。
数据平衡过程的要求
1.数据平衡不会导致数据块减少、数据块备份丢失。
2.管理员可以中止数据平衡进程。
3.每次数据块移动的大小应该是可控的，这样可以放置阻塞网络。
4.namenode不会因为数据平衡服务而导致过于繁忙。
数据自动平衡原理
由于使用了平衡算法，导致数据平衡是一个迭代的、周而复始的过程。每一次迭代的最终目的
是让高负载的机器能够降低数据负载，所以数据平衡会最大程度上地使用网络带宽。

数据平衡流程交互图

步骤分析如下：

1、数据均衡服务（Rebalancing Server）首先要求 NameNode 生成 DataNode 数据分布分析报告,获取每个DataNode磁盘使用情况
2、Rebalancing Server汇总需要移动的数据分布情况，计算具体数据块迁移路线图。数据块迁移路线图，确保网络内最短路径
3、开始数据块迁移任务，Proxy Source Data Node复制一块需要移动数据块
4、将复制的数据块复制到目标DataNode上
5、删除原始数据块
6、目标DataNode向Proxy Source Data Node确认该数据块迁移完成
7、Proxy Source Data Node向Rebalancing Server确认本次数据块迁移完成。然后继续执行这个过程，直至集群达到数据均衡标准

实际操作
1.切换到hdfs用户

[root@hadoop-master ~]# su - hdfs
2.查看当前的数据分布情况
[hdfs@hadoop-master ~]$ hdfs dfsadmin -report > /tmp/bq
[hdfs@hadoop-master ~]$ cat /tmp/bq 
Configured Capacity: 273287419086 (254.52 GB)
Present Capacity: 209643254756 (195.25 GB)
DFS Remaining: 199579415524 (185.87 GB)
DFS Used: 10063839232 (9.37 GB)
DFS Used%: 4.80%
Under replicated blocks: 0
Blocks with corrupt replicas: 0
Missing blocks: 0
Missing blocks (with replication factor 1): 0

配置容量：273287419086（254.52 GB）
现有容量：209643254756（195.25 GB）
DFS剩余：199579415524（185.87 GB）
使用的DFS：10063839232（9.37 GB）
使用DFS％：4.80％
在复制块下：0
具有损坏副本的块：0
缺少块：0
缺少块（复制因子1）：0
-------------------------------------------------
Live datanodes (3):  实时数据节点（3）：

Name: 192.168.0.117:50010 (hadoop-node01)
Hostname: hadoop-node01
Rack: /default
Decommission Status : Normal
Configured Capacity: 91095806362 (84.84 GB)
DFS Used: 3354603520 (3.12 GB)
Non DFS Used: 12246245786 (11.41 GB)
DFS Remaining: 69809631564 (65.02 GB)
DFS Used%: 3.68%
DFS Remaining%: 76.63%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 10
Last contact: Mon Jan 21 10:45:24 CST 2019

名称：192.168.0.117：50010（hadoop-node01）
主机名：hadoop-node01
机架：/默认
退役状态：正常
配置容量：91095806362（84.84 GB）
使用的DFS：3354603520（3.12 GB）
非DFS使用：12246245786（11.41 GB）
剩余DFS：69809631564（65.02 GB）
使用DFS％：3.68％
DFS剩余％：76.63％
配置的缓存容量：4294967296（4 GB）
使用的缓存：0（0 B）
剩余高速缓存：4294967296（4 GB）
使用的缓存％：0.00％
剩余高速缓存％：100.00％
Xceivers：10
最后联系人：Mon Jan 21 10:45:24 CST 2019

Name: 192.168.0.118:50010 (hadoop-master)
Hostname: hadoop-master
Rack: /default
Decommission Status : Normal
Configured Capacity: 91095806362 (84.84 GB)
DFS Used: 3354632192 (3.12 GB)
Non DFS Used: 29517959578 (27.49 GB)
DFS Remaining: 52537889100 (48.93 GB)
DFS Used%: 3.68%
DFS Remaining%: 57.67%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 10
Last contact: Mon Jan 21 10:45:24 CST 2019

Name: 192.168.0.121:50010 (hadoop-node02)
Hostname: hadoop-node02
Rack: /default
Decommission Status : Normal
Configured Capacity: 91095806362 (84.84 GB)
DFS Used: 3354603520 (3.12 GB)
Non DFS Used: 4823982490 (4.49 GB)
DFS Remaining: 77231894860 (71.93 GB)
DFS Used%: 3.68%
DFS Remaining%: 84.78%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 10
Last contact: Mon Jan 21 10:45:24 CST 2019

3.使用命令平衡数据
[hdfs@hadoop-master ~]$ hdfs balancer
19/01/21 10:49:19 INFO balancer.Balancer: namenodes  = [hdfs://vg-cdh-test]
19/01/21 10:49:19 INFO balancer.Balancer: parameters = Balancer.Parameters [BalancingPolicy.Node, threshold = 10.0, max idle iteration = 5, number of nodes to be excluded = 0, number of nodes to be included = 0, run during upgrade = false]
Time Stamp               Iteration#  Bytes Already Moved  Bytes Left To Move  Bytes Being Moved
19/01/21 10:49:21 INFO net.NetworkTopology: Adding a new node: /default/192.168.0.117:50010
19/01/21 10:49:21 INFO net.NetworkTopology: Adding a new node: /default/192.168.0.118:50010
19/01/21 10:49:21 INFO net.NetworkTopology: Adding a new node: /default/192.168.0.121:50010
19/01/21 10:49:21 INFO balancer.Balancer: 0 over-utilized: []
19/01/21 10:49:21 INFO balancer.Balancer: 0 underutilized: []
The cluster is balanced. Exiting...
2019-1-21 10:49:21                0                  0 B                 0 B               -1 B
2019-1-21 10:49:21       Balancing took 2.738 seconds
4.查看数据平衡后的数据分布情况
[hdfs@hadoop-master ~]$ hdfs dfsadmin -report > /tmp/bh
[hdfs@hadoop-master ~]$ cat /tmp/bh
Configured Capacity: 273287419086 (254.52 GB)
Present Capacity: 209660106924 (195.26 GB)
DFS Remaining: 199596266468 (185.89 GB)
DFS Used: 10063840456 (9.37 GB)
DFS Used%: 4.80%
Under replicated blocks: 0
Blocks with corrupt replicas: 0
Missing blocks: 0
Missing blocks (with replication factor 1): 0

-------------------------------------------------
Live datanodes (3):

Name: 192.168.0.117:50010 (hadoop-node01)
Hostname: hadoop-node01
Rack: /default
Decommission Status : Normal
Configured Capacity: 91095806362 (84.84 GB)
DFS Used: 3354603928 (3.12 GB)
Non DFS Used: 12246663170 (11.41 GB)
DFS Remaining: 69809213772 (65.01 GB)
DFS Used%: 3.68%
DFS Remaining%: 76.63%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 10
Last contact: Mon Jan 21 10:50:10 CST 2019

Name: 192.168.0.118:50010 (hadoop-master)
Hostname: hadoop-master
Rack: /default
Decommission Status : Normal
Configured Capacity: 91095806362 (84.84 GB)
DFS Used: 3354632600 (3.12 GB)
Non DFS Used: 29501419522 (27.48 GB)
DFS Remaining: 52554428748 (48.95 GB)
DFS Used%: 3.68%
DFS Remaining%: 57.69%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 10
Last contact: Mon Jan 21 10:50:10 CST 2019

Name: 192.168.0.121:50010 (hadoop-node02)
Hostname: hadoop-node02
Rack: /default
Decommission Status : Normal
Configured Capacity: 91095806362 (84.84 GB)
DFS Used: 3354603928 (3.12 GB)
Non DFS Used: 4823252994 (4.49 GB)
DFS Remaining: 77232623948 (71.93 GB)
DFS Used%: 3.68%
DFS Remaining%: 84.78%
Configured Cache Capacity: 4294967296 (4 GB)
Cache Used: 0 (0 B)
Cache Remaining: 4294967296 (4 GB)
Cache Used%: 0.00%
Cache Remaining%: 100.00%
Xceivers: 10
Last contact: Mon Jan 21 10:50:10 CST 2019
————————————————————————————————————————————————————————————————————————————————
5.对比数据平衡前后的报告信息
[hdfs@hadoop-master ~]$ diff /tmp/bq /tmp/bh
2,4c2,4
< Present Capacity: 209643254756 (195.25 GB)
< DFS Remaining: 199579415524 (185.87 GB)
< DFS Used: 10063839232 (9.37 GB)
---
> Present Capacity: 209660106924 (195.26 GB)
> DFS Remaining: 199596266468 (185.89 GB)
> DFS Used: 10063840456 (9.37 GB)
19,21c19,21
< DFS Used: 3354603520 (3.12 GB)
< Non DFS Used: 12246245786 (11.41 GB)
< DFS Remaining: 69809631564 (65.02 GB)
---
> DFS Used: 3354603928 (3.12 GB)
> Non DFS Used: 12246663170 (11.41 GB)
> DFS Remaining: 69809213772 (65.01 GB)
30c30
< Last contact: Mon Jan 21 10:45:24 CST 2019
---
> Last contact: Mon Jan 21 10:50:10 CST 2019
38,40c38,40
< DFS Used: 3354632192 (3.12 GB)
< Non DFS Used: 29517959578 (27.49 GB)
< DFS Remaining: 52537889100 (48.93 GB)
---
> DFS Used: 3354632600 (3.12 GB)
> Non DFS Used: 29501419522 (27.48 GB)
> DFS Remaining: 52554428748 (48.95 GB)
42c42
< DFS Remaining%: 57.67%
---
> DFS Remaining%: 57.69%
49c49
< Last contact: Mon Jan 21 10:45:24 CST 2019
---
> Last contact: Mon Jan 21 10:50:10 CST 2019
57,59c57,59
< DFS Used: 3354603520 (3.12 GB)
< Non DFS Used: 4823982490 (4.49 GB)
< DFS Remaining: 77231894860 (71.93 GB)
---
> DFS Used: 3354603928 (3.12 GB)
> Non DFS Used: 4823252994 (4.49 GB)
> DFS Remaining: 77232623948 (71.93 GB)
68c68
< Last contact: Mon Jan 21 10:45:24 CST 2019
---
> Last contact: Mon Jan 21 10:50:10 CST 2019

在生产上实际的操作如下：
hdfs dfsadmin -fs hdfs://uhadoop-mzwc2w-master2:8020 -setBalancerBandwidth 3145728000
[hadoop@uhadoop-mzwc2w-master1 ~]$ hdfs dfsadmin -fs hdfs://uhadoop-mzwc2w-master2:8020 -setBalancerBandwidth 3145728000
Balancer bandwidth is set to 3145728000
[hadoop@uhadoop-mzwc2w-master1 ~]$ hdfs dfsadmin -fs hdfs://uhadoop-mzwc2w-master1:8020 -setBalancerBandwidth 3145728000
Balancer bandwidth is set to 3145728000
//一定要2个节点namenode节点 master1 master2 都要执行 

在生产上2019/7/22 星期一 我在master1 和master2 都执行balancer 
[hadoop@uhadoop-mzwc2w-master1 majihui0718]$ nohup hdfs balancer > balancer.log & //生产上这样处理
[hadoop@uhadoop-mzwc2w-master2 majihui0722]$ pwd
/home/hadoop/majihui0722
[hadoop@uhadoop-mzwc2w-master2 majihui0722]$ ll
total 596
-rw-r--r-- 1 hadoop wheel 609794 Jul 22 14:11 balancer.log

我们是1000M的网，给300M的带宽用于datanode的数据balance

参考链接
https://www.cnblogs.com/qingyunzong/p/8535995.html
参考链接
HDFS balance策略详解 https://www.jianshu.com/p/f7c1cd476601

名称栏目：hdfs使用手册balancer（数据平衡）命令详解
新闻来源：http://kswjz.com/article/piesgg.html