[
https://issues.apache.org/jira/browse/HDFS-395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13065530#comment-13065530
]
Todd Lipcon commented on HDFS-395:
----------------------------------
bq. Todd, please correct me if I am wrong, but I don't see that this is
happening in FSDataset.invalidate().
Ah, it seems we have three separate but similar AsyncDiskServices in Hadoop :)
The MRAsyncDiskService class from MAPREDUCE-1302 uses a separate "toBeDeleted"
directory as described above - I thought we used the same technique in the HDFS
side, but it appears it's just a deferred delete of the file in the same
location as you described.
Can we share some code here? There's already another AsyncDiskService
superclass in common.
> 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
