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HBase >> mail # user >> HBase CheckSum vs Hadoop CheckSum

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RE: HBase CheckSum vs Hadoop CheckSum
I was typing a reply and by the time Liang replied :)
Ya agree with him.  It is only the HDFS client (At RS) not doing the checksum verification based on the HDFS stored checksum.
Instead HBase only check for the correctness by comparing with stored checksum values. Still the periodic operation of block scanning at HDFS will continue. We can turn this OFF by configuring this period with a -ve value I think.

Sent: Tuesday, February 26, 2013 5:54 PM
Subject: 答复: HBase CheckSum vs Hadoop CheckSum

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发件人: Jean-Marc Spaggiari [[EMAIL PROTECTED]]
发送时间: 2013年2月26日 20:03
收件人: user
主题: HBase CheckSum vs Hadoop CheckSum


Quick question.

When we are activating the short circuit read in HBase, it's
recommanded to activate the HBase checksum instead of Hadoop ones.
This is done in the HBase configuration.

I'm wondering what is the impact on the DataNode Block Scanner.

Is it going to be stopped because checksums can't be used anymore? Or
will Hadoop continue to store its own checksum and use them but it's
just that HBase will not look at them anymore and will store and use
its own checksums?
[liang xie]: yes, still store checksum in meta file in current community version.
btw, facebook's hadoop-fb20 branch has an inline checksum feature,IIRC

Since it's an HBase configuration (hbase.regionserver.checksum.verify)
I'm expecting this to not have any impact on the Block Scanner, but
I'm looking for a confirmation.
[liang xie]: yes, no impact on hdfs's DataBlockScanner, you can check
detail in datanode's BlockPoolSliceScanner.verifyBlock():
        blockSender = new BlockSender(block, 0, -1, false, true, true,
            datanode, null);