close
Warning:
Can't synchronize with repository "(default)" (Unsupported version control system "svn": /usr/lib/python2.7/dist-packages/libsvn/_repos.so: failed to map segment from shared object: Cannot allocate memory). Look in the Trac log for more information.
- Timestamp:
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Apr 1, 2009, 6:10:58 PM (15 years ago)
- Author:
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waue
- Comment:
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--
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55 | 55 | }}} |
56 | 56 | |
57 | | 不知道安全模式有何作用?? |
| 57 | === 安全模式的作用=== |
| 58 | * NameNode啟動時會從fsimage和edits日誌文件中裝載文件系統的狀態信息,接著它等待各個DataNode向它報告它們各自的數據塊狀態,這樣,NameNode就不會過早地開始複製數據塊,即使在副本充足的情況下。 |
| 59 | * 這個階段,NameNode處於安全模式下。NameNode的安全模式本質上是HDFS集群的一種只讀模式,此時集群不允許任何對文件系統或者數據塊修改的操作。通常NameNode會在開始階段自動地退出安全模式。 |
| 60 | * 如果需要,你也可以通過'bin/hadoop dfsadmin -safemode'命令顯式地將HDFS置於安全模式。NameNode首頁會顯示當前是否處於安全模式。關於安全模式的更多介紹和配置信息請參考JavaDoc:setSafeMode()。 |
58 | 61 | |
59 | 62 | == -finalizeUpgrade == |
… |
… |
|
83 | 86 | }}} |
84 | 87 | |
| 88 | = balancer = |
| 89 | 用於分析數據塊分佈和重新平衡DataNode上的數據分佈 |
| 90 | |
| 91 | {{{ |
| 92 | $ bin/hadoop balancer |
| 93 | |
| 94 | Time Stamp Iteration# Bytes Already Moved Bytes Left To Move Bytes Being Moved |
| 95 | |
| 96 | 09/04/01 18:00:08 INFO net.NetworkTopology: Adding a new node: /default-rack/140.110.138.191:50010 |
| 97 | |
| 98 | 09/04/01 18:00:08 INFO net.NetworkTopology: Adding a new node: /default-rack/140.110.141.129:50010 |
| 99 | |
| 100 | 09/04/01 18:00:08 INFO dfs.Balancer: 0 over utilized nodes: |
| 101 | |
| 102 | 09/04/01 18:00:08 INFO dfs.Balancer: 0 under utilized nodes: |
| 103 | |
| 104 | The cluster is balanced. Exiting... |
| 105 | |
| 106 | Balancing took 186.0 milliseconds |
| 107 | }}} |
| 108 | |
| 109 | = 機架感知(Rack awareness) = |
| 110 | 據說是設定某個參數 dfs.network.script ,旦目前為止還是不知道這個參數在哪 |
| 111 | |
85 | 112 | == References == |
86 | 113 | * http://www.michael-noll.com/wiki/Running_Hadoop_On_Ubuntu_Linux_(Multi-Node_Cluster) |