[jira] Commented: (HADOOP-64) DataNode should be capable of managing multiple volumes

["Johan Oskarson (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/HADOOP-64?page=comments#action_12420585 ] 

Johan Oskarson commented on HADOOP-64:
--------------------------------------

Noticed there's an unanswered question in the comment above.
How well does hadoop handle multiple volumes?
Since it starts one datanode per volume, is there a risk (even though it's a small risk) that a file with replication level 3 might end up with one block on one node, if said node have >=3 volumes?

> DataNode should be capable of managing multiple volumes
> -------------------------------------------------------
>
>          Key: HADOOP-64
>          URL: http://issues.apache.org/jira/browse/HADOOP-64
>      Project: Hadoop
>         Type: Improvement

>   Components: dfs
>     Versions: 0.2.0
>     Reporter: Sameer Paranjpye
>     Assignee: Konstantin Shvachko
>     Priority: Minor
>      Fix For: 0.5.0

>
> The dfs Datanode can only store data on a single filesystem volume. When a node runs its disks JBOD this means running a Datanode per disk on the machine. While the scheme works reasonably well on small clusters, on larger installations (several 100 nodes) it implies a very large number of Datanodes with associated management overhead in the Namenode.
> The Datanod should be enhanced to be able to handle multiple volumes on a single machine.

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