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From "dhruba borthakur (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5074) support checksums in HBase block cache
Date Tue, 20 Dec 2011 06:15:30 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13172967#comment-13172967
] 

dhruba borthakur commented on HBASE-5074:
-----------------------------------------

The corresponding HDFS jira is HDFS-2699.

Another alternative proposal is to store store a checksum in the block header of every hbase
block. HBase will make a pread(noChecksumVerify) call to hdfs for random reads. Once the block
is read into the hbase cache, it will verify the checksum and if not valid, have to use a
new HDFS api to read in contents from another hdfs replica.
                
> support checksums in HBase block cache
> --------------------------------------
>
>                 Key: HBASE-5074
>                 URL: https://issues.apache.org/jira/browse/HBASE-5074
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            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 into the HBase block cache 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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