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https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13215084#comment-13215084
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Phabricator commented on HBASE-5074:
------------------------------------

dhruba has commented on the revision "[jira] [HBASE-5074] Support checksums in 
HBase block cache".

INLINE COMMENTS
  src/main/java/org/apache/hadoop/hbase/io/hfile/ChecksumUtil.java:73 Actually, 
a new checksum object is created by every invocation of 
ChecksumType.getChecksumObject(), so it should be thread-safe
  src/main/java/org/apache/hadoop/hbase/fs/HFileSystem.java:120 doing it

  src/main/java/org/apache/hadoop/hbase/fs/HFileSystem.java:164 will 
restructure the comment, this feature is  switched on by default.

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

                
> 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, D1521.2.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
>
>
> 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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