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https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13218470#comment-13218470
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stack commented on HBASE-5074:
------------------------------

@Dhruba Its good trying for PureJavaCrc32 first.  Get rid of the WARN w/ thread 
dump I'd say especially as is where it comes after reporting we're not going to 
use PureJavaCrc32.  The feature does seem to be on by default but it would be 
nice to know it w/o having to go to ganglia graphs to figure my i/o loading to 
see whether or not this feature is enabled -- going to ganglia would be useless 
anyways in case where I've no history w/ an hbase read load -- so some kind of 
log output might be useful?  Good on you D.
                
> 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, D1521.10.patch, 
> D1521.10.patch, D1521.10.patch, D1521.10.patch, D1521.10.patch, 
> D1521.2.patch, D1521.2.patch, D1521.3.patch, D1521.3.patch, D1521.4.patch, 
> D1521.4.patch, D1521.5.patch, D1521.5.patch, D1521.6.patch, D1521.6.patch, 
> D1521.7.patch, D1521.7.patch, D1521.8.patch, D1521.8.patch, D1521.9.patch, 
> D1521.9.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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