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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7208) NN doesn't schedule replication when a DN storage fails
Date Wed, 08 Oct 2014 06:16:33 GMT
Ming Ma created HDFS-7208:
-----------------------------

             Summary: 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
            Reporter: Ming Ma


We found the following problem. Somehow 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 fails. 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.
{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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