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https://issues.apache.org/jira/browse/HDFS-1362?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007187#comment-13007187
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Allen Wittenauer commented on HDFS-1362:
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I look at it like this:
Is there a downside to supporting this functionality? Just because it is there
doesn't mean one has to use it. It is trivial to come up with a practical use
case (front-side serving HBase machines). [I'm avoiding the temptation to make
a snide comment about Federation here. ;) ]
It is also worth pointing out that other operating systems have better IO
subsystems for hot swapping. So while it may not work on one particular
config, that doesn't mean all of them are cursed.
FWIW, RAID-0, mounting, newfs'ing, etc is irrelevant. If HDFS talked to raw
disks this would matter; Hadoop talks to file systems so any hardware/software
OS config would already need to be in place anyway. For small grids where you
can do replacements, this functionality makes sense.
> Provide volume management functionality for DataNode
> ----------------------------------------------------
>
> Key: HDFS-1362
> URL: https://issues.apache.org/jira/browse/HDFS-1362
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: data-node
> Affects Versions: 0.23.0
> Reporter: Wang Xu
> Assignee: Wang Xu
> Fix For: 0.23.0
>
> Attachments: DataNode Volume Refreshment in HDFS-1362.pdf,
> HDFS-1362.4_w7001.txt, HDFS-1362.5.patch, HDFS-1362.6.patch,
> HDFS-1362.7.patch, HDFS-1362.txt, Provide_volume_management_for_DN_v1.pdf
>
>
> The current management unit in Hadoop is a node, i.e. if a node failed, it
> will be kicked out and all the data on the node will be replicated.
> As almost all SATA controller support hotplug, we add a new command line
> interface to datanode, thus it can list, add or remove a volume online, which
> means we can change a disk without node decommission. Moreover, if the failed
> disk still readable and the node has enouth space, it can migrate data on the
> disks to other disks in the same node.
> A more detailed design document will be attached.
> The original version in our lab is implemented against 0.20 datanode
> directly, and is it better to implemented it in contrib? Or any other
> suggestion?
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