hdfs使用手冊balancer（數據平衡）命令詳解

2019/1/21 星期一

2.3.1. balancer
運行一個集群平衡工具。管理員可以通過按Ctrl+C鍵停止再平衡過程。
數據平衡的需求
HDFS數據不平衡的原因
1.某個DataNode機器內硬盤存儲達到飽和值。
2.集群內新增、刪除節點。
數據不平衡的影響
1.Map任務可能會被分配給沒有存儲數據的機器，結果是不能實現本地計算，最終會導致網絡
帶寬的消耗。
2.當一些數據節點數據完全滿載時，新的數據塊只會被存放在有空余數據的節點機器上，造成了并行讀取的可能性。
數據平衡過程的要求
1.數據平衡不會導致數據塊減少、數據塊備份丟失。
2.管理員可以中止數據平衡進程。
3.每次數據塊移動的大小應該是可控的，這樣可以放置阻塞網絡。
4.namenode不會因為數據平衡服務而導致過于繁忙。
數據自動平衡原理
由于使用了平衡算法，導致數據平衡是一個迭代的、周而復始的過程。每一次迭代的最終目的
是讓高負載的機器能夠降低數據負載，所以數據平衡會最大程度上地使用網絡帶寬。

數據平衡流程交互圖

步驟分析如下：

1、數據均衡服務（Rebalancing Server）首先要求 NameNode 生成 DataNode 數據分布分析報告,獲取每個DataNode磁盤使用情況
2、Rebalancing Server匯總需要移動的數據分布情況，計算具體數據塊遷移路線圖。數據塊遷移路線圖，確保網絡內最短路徑
3、開始數據塊遷移任務，Proxy Source Data Node復制一塊需要移動數據塊
4、將復制的數據塊復制到目標DataNode上
5、刪除原始數據塊
6、目標DataNode向Proxy Source Data Node確認該數據塊遷移完成
7、Proxy Source Data Node向Rebalancing Server確認本次數據塊遷移完成。然后繼續執行這個過程，直至集群達到數據均衡標準

實際操作
1.切換到hdfs用戶

[root@hadoop-master ~]# su - hdfs
2.查看當前的數據分布情況
[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）
現有容量：209643254756（195.25 GB）
DFS剩余：199579415524（185.87 GB）
使用的DFS：10063839232（9.37 GB）
使用DFS％：4.80％
在復制塊下：0
具有損壞副本的塊：0
缺少塊：0
缺少塊（復制因子1）：0
-------------------------------------------------
Live datanodes (3):  實時數據節點（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

名稱：192.168.0.117：50010（hadoop-node01）
主機名：hadoop-node01
機架：/默認
退役狀態：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％
配置的緩存容量：4294967296（4 GB）
使用的緩存：0（0 B）
剩余高速緩存：4294967296（4 GB）
使用的緩存％：0.00％
剩余高速緩存％：100.00％
Xceivers：10
最后聯系人：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.使用命令平衡數據
[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.查看數據平衡后的數據分布情況
[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.對比數據平衡前后的報告信息
[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

在生產上實際的操作如下：
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個節點namenode節點 master1 master2 都要執行 

在生產上2019/7/22 星期一 我在master1 和master2 都執行balancer 
[hadoop@uhadoop-mzwc2w-master1 majihui0718]$ nohup hdfs balancer > balancer.log & //生產上這樣處理
[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

我們是1000M的網，給300M的帶寬用于datanode的數據balance

參考鏈接
https://www.cnblogs.com/qingyunzong/p/8535995.html
參考鏈接
HDFS balance策略詳解 https://www.jianshu.com/p/f7c1cd476601