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https://issues.apache.org/jira/browse/HDFS-8578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15042012#comment-15042012
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Chris Trezzo commented on HDFS-8578:
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One big spot where I see the memory footprint potentially increasing is in
{{DataStorage#linkBlocksHelper}}. We build a list of {{LinkArgs}} called
{{idBasedLayoutSingleLinks}}. This has 1 LinkArgs object per hard-link that we
will need to create. Now with the parallelism we will have potentially 12 * 3 =
36 of these lists in memory at the same time. In other words, 1 LinkArgs object
in memory for every hard-link we have to create on the data node.
> On upgrade, Datanode should process all storage/data dirs in parallel
> ---------------------------------------------------------------------
>
> Key: HDFS-8578
> URL: https://issues.apache.org/jira/browse/HDFS-8578
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Reporter: Raju Bairishetti
> Assignee: Vinayakumar B
> Priority: Critical
> Attachments: HDFS-8578-01.patch, HDFS-8578-02.patch,
> HDFS-8578-03.patch, HDFS-8578-04.patch, HDFS-8578-05.patch,
> HDFS-8578-06.patch, HDFS-8578-07.patch, HDFS-8578-08.patch,
> HDFS-8578-09.patch, HDFS-8578-10.patch, HDFS-8578-11.patch,
> HDFS-8578-12.patch, HDFS-8578-branch-2.6.0.patch
>
>
> Right now, during upgrades datanode is processing all the storage dirs
> sequentially. Assume it takes ~20 mins to process a single storage dir then
> datanode which has ~10 disks will take around 3hours to come up.
> *BlockPoolSliceStorage.java*
> {code}
> for (int idx = 0; idx < getNumStorageDirs(); idx++) {
> doTransition(datanode, getStorageDir(idx), nsInfo, startOpt);
> assert getCTime() == nsInfo.getCTime()
> : "Data-node and name-node CTimes must be the same.";
> }
> {code}
> It would save lots of time during major upgrades if datanode process all
> storagedirs/disks parallelly.
> Can we make datanode to process all storage dirs parallelly?
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