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https://issues.apache.org/jira/browse/HDFS-2699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171601#comment-13171601
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dhruba borthakur commented on HDFS-2699:
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There are various alternatie like you proposed. The advantage of an application
level checksum (at the hbase block level) sounds easy to do. The disadvantage
is that hdfs still have to do generate/store checksums to periodically validate
data that is not accessed for a long time.
> by supporting two block format simultaneously at the expense of code
> complexity
are u saying that the same data is stored in two places? One is the current
format and another is the format with inline checksums?
> Store data and checksums together in block file
> -----------------------------------------------
>
> Key: HDFS-2699
> URL: https://issues.apache.org/jira/browse/HDFS-2699
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
>
> The current implementation of HDFS stores the data in one block file and the
> metadata(checksum) in another block file. This means that every read from
> HDFS actually consumes two disk iops, one to the datafile and one to the
> checksum file. This is a major problem for scaling HBase, because HBase is
> usually bottlenecked on the number of random disk iops that the
> storage-hardware offers.
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