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From "Tsz Wo Nicholas Sze (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-7208) NN doesn't schedule replication when a DN storage fails
Date Thu, 16 Oct 2014 03:42:35 GMT

     [ https://issues.apache.org/jira/browse/HDFS-7208?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Tsz Wo Nicholas Sze updated HDFS-7208:
    Hadoop Flags: Reviewed

+1 patch looks good.

> 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
>         Attachments: HDFS-7208-2.patch, HDFS-7208-3.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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