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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 Tue, 25 Sep 2012 02:24:08 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6868?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13462368#comment-13462368
] 

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

bq. The patch permanently ties the checksumming feature to local short circuit

Yep, this is the reality currently. When that changes, we should change the patch, methinks.

On setting both config options... This would lead to issue reported here that HLogs are not
checksummed.

I think with the proposed change we get best we can get right now. If HDFS is setup such that
disabling checksumming would have a benefit, it is switched on and enabled correctly in HBase.

Once HDFS-3429 is in (and in a mainstream HDFS release, which might be a while) we should
rethink this.
(Just doing this for 0.94 and leave 0.96 the way it is seems OK too.)

                
> 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
>
>
> 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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