hadoop-hdfs-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Tomasz Nykiel (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-395) DFS Scalability: Incremental block reports
Date Thu, 28 Jul 2011 00:47:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13072126#comment-13072126
] 

Tomasz Nykiel commented on HDFS-395:
------------------------------------

Suresh,

Thanks for the review. I addressed all comments except one.
Accessing pendingReceivedRequests in offerService is fine, since we do not modify it.
I made it volatile so it's not cached thread-locally. 
In the worst case, there might a delay of one loop iteration of offerservice, when a block
is already added to the list but pendingReceivedRequests not updated.

Regarding your question about deletion. 
I think we concluded that this issue should be updated separately, as it is not strictly related
to explicit ACK. 

I will also have to run the JUnit tests.

> DFS Scalability: Incremental block reports
> ------------------------------------------
>
>                 Key: HDFS-395
>                 URL: https://issues.apache.org/jira/browse/HDFS-395
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: dhruba borthakur
>            Assignee: Tomasz Nykiel
>         Attachments: blockReportPeriod.patch, explicitAcks.patch-3, explicitDeleteAcks.patch
>
>
> I have a cluster that has 1800 datanodes. Each datanode has around 50000 blocks and sends
a block report to the namenode once every hour. This means that the namenode processes a block
report once every 2 seconds. Each block report contains all blocks that the datanode currently
hosts. This makes the namenode compare a huge number of blocks that practically remains the
same between two consecutive reports. This wastes CPU on the namenode.
> The problem becomes worse when the number of datanodes increases.
> One proposal is to make succeeding block reports (after a successful send of a full block
report) be incremental. This will make the namenode process only those blocks that were added/deleted
in the last period.

--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira

        

Mime
View raw message