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https://issues.apache.org/jira/browse/HDFS-10586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15393729#comment-15393729
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Alberic Liu commented on HDFS-10586:
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我也一样，写和读可以，但挂掉3个节点就读不出来，明天看看代码，哪有问题。
> Erasure Code misfunctions when 3 DataNode down
> ----------------------------------------------
>
> Key: HDFS-10586
> URL: https://issues.apache.org/jira/browse/HDFS-10586
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: erasure-coding
> Affects Versions: 3.0.0-alpha1
> Environment: 9 DataNode and 1 NameNode, Erasured code policy is
> set as "6--3", When 3 DataNode down, erasured code fails and an exception
> is thrown
> Reporter: gao shan
>
> The following is the steps to reproduce:
> 1) hadoop fs -mkdir /ec
> 2) set erasured code policy as "6-3"
> 3) "write" data by :
> time hadoop jar
> /opt/hadoop/hadoop-3.0.0-SNAPSHOT/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-3.0.0-SNAPSHOT.jar
> TestDFSIO -D test.build.data=/ec -write -nrFiles 30 -fileSize 12288
> -bufferSize 1073741824
> 4) Manually down 3 nodes. Kill the threads of "datanode" and "nodemanager"
> in 3 DataNode.
> 5) By using erasured code to "read" data by:
> time hadoop jar
> /opt/hadoop/hadoop-3.0.0-SNAPSHOT/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-3.0.0-SNAPSHOT.jar
> TestDFSIO -D test.build.data=/ec -read -nrFiles 30 -fileSize 12288
> -bufferSize 1073741824
> then the failure occurs and the exception is thrown as:
> INFO mapreduce.Job: Task Id : attempt_1465445965249_0008_m_000034_2, Status :
> FAILED
> Error: java.io.IOException: 4 missing blocks, the stripe is: Offset=0,
> length=8388608, fetchedChunksNum=0, missingChunksNum=4
> at
> org.apache.hadoop.hdfs.DFSStripedInputStream$StripeReader.checkMissingBlocks(DFSStripedInputStream.java:614)
> at
> org.apache.hadoop.hdfs.DFSStripedInputStream$StripeReader.readParityChunks(DFSStripedInputStream.java:647)
> at
> org.apache.hadoop.hdfs.DFSStripedInputStream$StripeReader.readStripe(DFSStripedInputStream.java:762)
> at
> org.apache.hadoop.hdfs.DFSStripedInputStream.readOneStripe(DFSStripedInputStream.java:316)
> at
> org.apache.hadoop.hdfs.DFSStripedInputStream.readWithStrategy(DFSStripedInputStream.java:450)
> at org.apache.hadoop.hdfs.DFSInputStream.read(DFSInputStream.java:941)
> at java.io.DataInputStream.read(DataInputStream.java:149)
> at org.apache.hadoop.fs.TestDFSIO$ReadMapper.doIO(TestDFSIO.java:531)
> at org.apache.hadoop.fs.TestDFSIO$ReadMapper.doIO(TestDFSIO.java:508)
> at org.apache.hadoop.fs.IOMapperBase.map(IOMapperBase.java:134)
> at org.apache.hadoop.fs.IOMapperBase.map(IOMapperBase.java:37)
> at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:54)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:453)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343)
> at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:174)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:422)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1669)
> at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:168)
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