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https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13222898#comment-13222898
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Phabricator commented on HBASE-5074:
------------------------------------

mbautin has accepted the revision "[jira] [HBASE-5074] Support checksums in 
HBase block cache".

  @dhruba: looks good! A few minor comments inline.

  Also, I still think there is some code duplication between TestHFileBlock and 
TestHFileBlockCompatibility that we could get rid of, but we can do that in a 
separate patch.

  Could you please attach the final patch to the JIRA and run it on Hadoop QA?

INLINE COMMENTS
  src/main/java/org/apache/hadoop/hbase/io/hfile/AbstractHFileReader.java:48 
s/do do/do/
  src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java:1242 do do -> 
do
  
src/test/java/org/apache/hadoop/hbase/io/hfile/TestHFileBlockCompatibility.java:161-174
 It would be great to factor out the common part of this hard-coded gzip blob 
so that it is not repeated in TestHFileBlock and here.

  This is an example of what I meant in my comment regarding code duplication.

  Alternatively, we can remove code duplication in a follow-up patch.

REVISION DETAIL
  https://reviews.facebook.net/D1521

BRANCH
  svn

                
> 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
>             Fix For: 0.94.0
>
>         Attachments: D1521.1.patch, D1521.1.patch, D1521.10.patch, 
> D1521.10.patch, D1521.10.patch, D1521.10.patch, D1521.10.patch, 
> D1521.11.patch, D1521.11.patch, D1521.12.patch, D1521.12.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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