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From "stack (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4608) HLog Compression
Date Wed, 14 Mar 2012 04:29:51 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13228957#comment-13228957

stack commented on HBASE-4608:

bq. I noticed the size of sv4r25s8%3A60020.1331661889339.decompressed is different from that
of sv4r25s8%3A60020.1331661889339

Because it has metadata the original doesn't have.  When I compress it, it compresses down
to same size.  Notice that the decompressed and decompressed.again are same size because they
both have the new meata data.

bq. The sentence involving COMPRESSION_VERSION was in past tense but I don't see it in patch

Pardon me.  Should have uploaded v24.

Testing has turned up a minor issue... will upload v25 soon.

bq. In my opinion, this version corresponds to the major version in my comment @ 13/Mar/12

Nope.  This is the global version that introduces compression.  No need of major/minor granularity,
and in particular major/minor on the compression feature itself.  Its overkill.

bq. I agree that both version and compression type should be checked. However, the order should
be checking compression type followed by checking version.

Nope.  First figure if we have a file that does compression.  Then figure what type of compression
the file does.
> HLog Compression
> ----------------
>                 Key: HBASE-4608
>                 URL: https://issues.apache.org/jira/browse/HBASE-4608
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Li Pi
>            Assignee: stack
>             Fix For: 0.94.0
>         Attachments: 4608-v19.txt, 4608-v20.txt, 4608-v22.txt, 4608v1.txt, 4608v13.txt,
4608v13.txt, 4608v14.txt, 4608v15.txt, 4608v16.txt, 4608v17.txt, 4608v18.txt, 4608v23.txt,
4608v24.txt, 4608v5.txt, 4608v6.txt, 4608v7.txt, 4608v8fixed.txt
> The current bottleneck to HBase write speed is replicating the WAL appends across different
datanodes. We can speed up this process by compressing the HLog. Current plan involves using
a dictionary to compress table name, region id, cf name, and possibly other bits of repeated
data. Also, HLog format may be changed in other ways to produce a smaller HLog.

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