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From "Allen Wittenauer (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2699) Store data and checksums together in block file
Date Sat, 17 Dec 2011 20:11:30 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2699?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13171660#comment-13171660
] 

Allen Wittenauer commented on HDFS-2699:
----------------------------------------

Would it make sense to make the equivalent of a logging device instead?  In other words, put
the meta files on a dedicated fast/small disk to segregate them from the actual data blocks?
 Besides just being able to pick a better storage medium, it might potentially allow for better
caching strategies at the OS level (depending upon the OS of course).
                
> 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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