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Date: Thu, 6 Dec 2012 22:40:35 +0000 (UTC)
From: "Andy Isaacson (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12618208.1354218040367.91.1354833635796@arcas>
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Subject: [jira] [Commented] (HDFS-4239) Means of telling the datanode to
 stop using a sick disk
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    [ https://issues.apache.org/jira/browse/HDFS-4239?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13525888#comment-13525888 ] 

Andy Isaacson commented on HDFS-4239:
-------------------------------------

I created HDFS-4284 to track the BlockReaderLocal issue.
                
> 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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