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 Fri, 01 Jul 2011 21:17:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13058807#comment-13058807
] 

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

When the invalidate comes, the physical block file "blk_" is schedulaed for deletion asynchronously.
Without renaming, but with explicit deletion ACKs it could theoretically happen:

1. invalidate comes
2. delete ACK is sent
3. block report is constructed - it may still contain the block file because it's not deleted
4. asynchronous delete takes place.

So the NN would get contradicting information. 
If we just rename it to an invalid name e.g., "toDelete.blk_..." block report would not pick
it up.

> 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: dhruba borthakur
>         Attachments: blockReportPeriod.patch, 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