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https://issues.apache.org/jira/browse/HDFS-1120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13011229#comment-13011229
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Harsh J Chouraria commented on HDFS-1120:
-----------------------------------------
I've done some initial work for making the volume-block choosing policy
pluggable (so that methods other than round-robin may be provided).
The following is my initial interface design, and am looking for
comments/critique/etc. w.r.t. this ticket's scope, before I start pushing out
some tests + patches:
{code}
/**************************************************
* BlockVolumeChoosingPolicy allows a DataNode to
* specify what policy is to be used while choosing
* a volume for a block request.
*
***************************************************/
public interface BlockVolumeChoosingPolicy extends Configurable {
/**
* Returns a specific FSVolume after applying a suitable choice algorithm
* to place a given block, given a list of FSVolumes and the block
* size sought for storage.
* @param volumes - the array of FSVolumes that are available.
* @param blockSize - the size of the block for which a volume is sought.
* @return the chosen volume to store the block.
* @throws IOException when disks are unavailable or are full.
*/
public FSVolume chooseVolume(FSVolume[] volumes, long blockSize)
throws IOException;
}
{code}
This can be neatly used within FSVolumeSet.getNextVolume() [Maybe this too
needs to be renamed, since it may not make sense as 'next' once it becomes
pluggable]
Looking forward to a discussion.
P.s. I also posted this to hdfs-dev, but I guess most of Hadoop's devel
discussions occur on the JIRA itself?
> Make DataNode's block-to-device placement policy pluggable
> ----------------------------------------------------------
>
> Key: HDFS-1120
> URL: https://issues.apache.org/jira/browse/HDFS-1120
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node
> Reporter: Jeff Hammerbacher
> Assignee: Harsh J Chouraria
>
> As discussed on the mailing list, as the number of disk drives per server
> increases, it would be useful to allow the DataNode's policy for new block
> placement to grow in sophistication from the current round-robin strategy.
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