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From "Phabricator (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5074) support checksums in HBase block cache
Date Sat, 18 Feb 2012 01:06:01 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13210717#comment-13210717

Phabricator commented on HBASE-5074:

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

  I got about 15% through.  Will do rest later.  This stuff is great.

  src/main/java/org/apache/hadoop/hbase/HConstants.java:605 Nice doc.  Lets hoist up into
the reference manual on commit.
  src/main/java/org/apache/hadoop/hbase/fs/HFileSystem.java:1 Good.  I think its better having
it in here.
  src/main/java/org/apache/hadoop/hbase/fs/HFileSystem.java:115 I see we use this writing
the WAL. Reading we'll use whatever the readfs?   Do we need to expose this?  Or the getReadRS

  Or is it that you want different fs's for read and write?  If so, should this method be
called getWriteFS?
  src/main/java/org/apache/hadoop/hbase/fs/HFileSystem.java:129 Post creation, invoking this
method would have no effect?  If so, remove, and make this data member final?
  src/main/java/org/apache/hadoop/hbase/io/hfile/AbstractHFileReader.java:44 Why change this
comment?  Do we care how it does checksumming?
  src/main/java/org/apache/hadoop/hbase/io/hfile/AbstractHFileReader.java:49 Yeah, I wonder
if upper tiers need worry about this stuff?  Whether its checksummed or not?  Should they
just be talking about readfs vs writefs?  And then its up to the configuration as to what
the underlying fs does (in this case its just turning off hdfs checksumming).  Looks like
actual checksumming is over in HFileBlock... maybe HFile itself doesn't need to be concerned
w/ checksumming?

  No biggie.  Just a comment.


> 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,
> 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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