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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6868) Skip checksum is broke; are we double-checksumming by default?
Date Sat, 22 Sep 2012 22:42:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13461286#comment-13461286
] 

Lars Hofhansl commented on HBASE-6868:
--------------------------------------

So I am looking through the patch in HBASE-5074.

@LiuLei: Did you positively verify that we're not reading the checksums for the HLogs?

HBASE-5074 introduces HFileSystem, which has a getNoChecksumFs() method, as well as a getBackingFs()
method. The backingFs is not checksummed. Looks like for the HLog the backingFs is used, which
does not have checksums disabled.
                
> Skip checksum is broke; are we double-checksumming by default?
> --------------------------------------------------------------
>
>                 Key: HBASE-6868
>                 URL: https://issues.apache.org/jira/browse/HBASE-6868
>             Project: HBase
>          Issue Type: Bug
>          Components: HFile, wal
>    Affects Versions: 0.94.0, 0.94.1
>            Reporter: LiuLei
>            Priority: Blocker
>             Fix For: 0.94.3, 0.96.0
>
>
> The HFile contains checksums for decrease the iops, so when Hbase read HFile , that dont't
need to read the checksum from meta file of HDFS.  But HLog file of Hbase don't contain the
checksum, so when HBase read the HLog, that must read checksum from meta file of HDFS.  We
could  add setSkipChecksum per file to hdfs or we could write checksums into WAL if this skip
checksum facility is enabled 

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