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From "Zhihong Yu (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5074) support checksums in HBase block cache
Date Mon, 30 Jan 2012 05:35:10 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13195940#comment-13195940
] 

Zhihong Yu commented on HBASE-5074:
-----------------------------------

In HFileBlock.readBlockData(), once useHBaseChecksum is set to false, I don't see where it
would be set to true again.
At line 1613, if HDFS checksum verification was able to correct the problem,
1. should we re-enable useHBaseChecksum ?
2. I think we should log the fact that HDFS checksum verification worked.
{code}
     * @param pread whether to use HBase checksums. If HBase checksum is
     *          switched off, then use HDFS checksum.
{code}
Please correct the name of parameter above.
                
> 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
>         Attachments: D1521.1.patch, D1521.1.patch
>
>
> 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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