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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6868) Skip checksum is broke; are we double-checksumming by default?
Date Tue, 25 Sep 2012 04:41:08 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13462440#comment-13462440

stack commented on HBASE-6868:

+1 on patch.  Default is let hdfs worry about checksums.  No chance of dbl-checksumming. 
If you did enable HBASE-5074 hbase checksums and also enabled shortcircuit, you should be
good (you'll be doing an unwanted extra seek if you have to do a non-local until hdfs-3429
goes in but thats another issue).  Your setting of dfs.client.read.shortcircuit.skip.checksum
on the hfile fs, will make it so we avoid a dbl-checksum.  The new Configuration is important
before you set the boolean as you have it.  I think this is good for trunk and 0.94.

We should test starting a 0.94.2 on top of data written when the flag was true to see if we
skip over the hbase inserted checksums.

I can write a little note for the refguide on this after goes in.  Will also look at verifying

> 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
>         Attachments: 6868-0.96-idea.txt, 6868-0.96-v2.txt, 6868-0.96-v3.txt
> 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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