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From "Phabricator (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5074) support checksums in HBase block cache
Date Thu, 23 Feb 2012 22:15:50 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13215114#comment-13215114

Phabricator commented on HBASE-5074:

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

  @dhruba: going through the diff once again. Since you've updated the revision, submitting
existing comments against the previous version, and continuing with the new version.

  src/main/java/org/apache/hadoop/hbase/io/hfile/ChecksumUtil.java:131 Misspelling: "Minimun"
-> Minimum
  src/main/java/org/apache/hadoop/hbase/fs/HFileSystem.java:44-45 Can these two be made final
  src/main/java/org/apache/hadoop/hbase/io/hfile/ChecksumUtil.java:145 s/chuck/chunk/
  src/main/java/org/apache/hadoop/hbase/io/hfile/AbstractHFileReader.java:48 Fix javadoc:
do do -> do
  src/main/java/org/apache/hadoop/hbase/io/hfile/ChecksumUtil.java:38 Make this final, rename
to DUMMY_VALUE, because this is a constant, and make the length a factor of 16 to take advantage
of alignment.
  src/main/java/org/apache/hadoop/hbase/io/hfile/FixedFileTrailer.java:532 s/manor/major/
  src/main/java/org/apache/hadoop/hbase/io/hfile/HFile.java:157 This comment is misleading.
This is not something that defaults to the 16 K, but the default value itself. I think this
should say something about how a non-default value is specified.
  src/main/java/org/apache/hadoop/hbase/io/hfile/HFile.java:265-271 The additional constructor
should not be needed when https://issues.apache.org/jira/browse/HBASE-5442 goes in.
  src/main/java/org/apache/hadoop/hbase/io/hfile/HFile.java:409 Is it possible to obtain the
filesystem from the input stream rather than pass it as an additional parameter? Or is the
underlying filesystem of the input stream a regular one, as opposed to an HFileSystem?


> 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, 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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