[jira] [Commented] (HDFS-8578) On upgrade, Datanode should process all storage/data dirs in parallel

["Chris Trezzo (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-8578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15126809#comment-15126809 ] 

Chris Trezzo commented on HDFS-8578:
------------------------------------

[~szetszwo] [~vinayrpet]

One major issue I see with this patch is that we change the order of execution for some of the operations. For example, in DataStorage#loadStorageDirectory the hard-linking of directories now happens after the following:
{noformat}
      // 3. Update successfully loaded storage.
      setServiceLayoutVersion(getServiceLayoutVersion());
      writeProperties(sd);
{noformat}

This would present issues in the scenario where the data node fails after the above step, but before hard-linking actually occurs.

> 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-8578-13.patch, HDFS-8578-14.patch, HDFS-8578-15.patch, HDFS-8578-16.patch, HDFS-8578-17.patch, HDFS-8578-branch-2.6.0.patch, HDFS-8578-branch-2.7-001.patch, HDFS-8578-branch-2.7-002.patch, HDFS-8578-branch-2.7-003.patch, h8578_20151210.patch, h8578_20151211.patch, h8578_20151211b.patch, h8578_20151212.patch, h8578_20151213.patch, h8578_20160117.patch, h8578_20160128.patch, h8578_20160128b.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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