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https://issues.apache.org/jira/browse/HDFS-7208?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15026360#comment-15026360
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刘喆 commented on HDFS-7208:
--------------------------
Code in comment seems ugly, so I have added a patch file.
> NN doesn't schedule replication when a DN storage fails
> -------------------------------------------------------
>
> Key: HDFS-7208
> URL: https://issues.apache.org/jira/browse/HDFS-7208
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Reporter: Ming Ma
> Assignee: Ming Ma
> Fix For: 2.6.0
>
> Attachments: HDFS-7208-2.patch, HDFS-7208-3.patch,
> HDFS-7208-AdMaster.patch, HDFS-7208.patch
>
>
> We found the following problem. When a storage device on a DN fails, NN
> continues to believe replicas of those blocks on that storage are valid and
> doesn't schedule replication.
> A DN has 12 storage disks. So there is one blockReport for each storage. When
> a disk fails, # of blockReport from that DN is reduced from 12 to 11. Given
> dfs.datanode.failed.volumes.tolerated is configured to be > 0, NN still
> considers that DN healthy.
> 1. A disk failed. All blocks of that disk are removed from DN dataset.
>
> {noformat}
> 2014-10-04 02:11:12,626 WARN
> org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl: Removing
> replica BP-1748500278-xx.xx.xx.xxx-1377803467793:1121568886 on failed volume
> /data/disk6/dfs/current
> {noformat}
> 2. NN receives DatanodeProtocol.DISK_ERROR. But that isn't enough to have NN
> remove the DN and the replicas from the BlocksMap. In addition, blockReport
> doesn't provide the diff given that is done per storage.
> {noformat}
> 2014-10-04 02:11:12,681 WARN org.apache.hadoop.hdfs.server.namenode.NameNode:
> Disk error on DatanodeRegistration(xx.xx.xx.xxx,
> datanodeUuid=f3b8a30b-e715-40d6-8348-3c766f9ba9ab, infoPort=50075,
> ipcPort=50020,
> storageInfo=lv=-55;cid=CID-e3c38355-fde5-4e3a-b7ce-edacebdfa7a1;nsid=420527250;c=1410283484939):
> DataNode failed volumes:/data/disk6/dfs/current
> {noformat}
> 3. Run fsck on the file and confirm the NN's BlocksMap still has that replica.
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