stack created HDFS-4239:
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Summary: Means of telling the datanode to stop using a sick disk
Key: HDFS-4239
URL: https://issues.apache.org/jira/browse/HDFS-4239
Project: Hadoop HDFS
Issue Type: Improvement
Reporter: stack
If a disk has been deemed 'sick' -- i.e. not dead but wounded, failing
occasionally, or just exhibiting high latency -- your choices are:
1. Decommission the total datanode. If the datanode is carrying 6 or 12 disks
of data, especially on a cluster that is smallish -- 5 to 20 nodes -- the
rereplication of the downed datanode's data can be pretty disruptive,
especially if the cluster is doing low latency serving: e.g. hosting an hbase
cluster.
2. Stop the datanode, unmount the bad disk, and restart the datanode (You can't
unmount the disk while it is in use). This latter is better in that only the
bad disk's data is rereplicated, not all datanode data.
Is it possible to do better, say, send the datanode a signal to tell it stop
using a disk an operator has designated 'bad'. This would be like option #2
above minus the need to stop and restart the datanode. Ideally the disk would
become unmountable after a while.
Nice to have would be being able to tell the datanode to restart using a disk
after its been replaced.
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