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Date: Thu, 9 Feb 2012 07:35:01 +0000 (UTC)
From: "Phabricator (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-5074) support checksums in HBase block
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    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13204335#comment-13204335 ] 

Phabricator commented on HBASE-5074:
------------------------------------

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

  Took a look at a little piece of the patch.  It looks great.

INLINE COMMENTS
  src/main/java/org/apache/hadoop/hbase/HConstants.java:601 It looks like this feature will be on by default.  Good.
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:1 Should this class be in an fs package rather than in util?

  Nit.  HFileSystem seems overly generic.  Should it be HBaseFileSystem?

  Out of interest, is there a performance penalty that you know of going via FilterFileSystem?
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:40 How would this happen?   We'd look at the path for the object and do a different fs in here based off that?
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:49 Won't the master use this fs too?
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:50 configuration
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:74 cool
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:107 Who would want this?  Can we shut it down?
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:112 Its not the 'default' fs, it IS the fs?
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:167 cool
  src/main/java/org/apache/hadoop/hbase/util/HFileSystem.java:172 So we'll have nonrecursive w/ this method?  I'm not sure I follow.  This method will go away when filterfilesystem supports nonrecursive create?

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
>
>
> 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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