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From Jean-Marc Spaggiari <jean-m...@spaggiari.org>
Subject Re: HBase CheckSum vs Hadoop CheckSum
Date Tue, 26 Feb 2013 13:34:09 GMT
Thanks for your replies. Few seconds I was feeling unsecured ;)

Seems the default period for the DataBlockScanner is 3 weeks:
static final long DEFAULT_SCAN_PERIOD_HOURS = 21*24L;

And I have not found anyway to modify that. I will continue to search
and might drop a msg on hadoop list if I still don't find.

Thanks,

JM

2013/2/26 Anoop Sam John <anoopsj@huawei.com>:
> 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.
>
> -Anoop-
> ________________________________________
> From: 谢良 [xieliang@xiaomi.com]
> Sent: Tuesday, February 26, 2013 5:54 PM
> To: user@hbase.apache.org
> Subject: 答复: HBase CheckSum vs Hadoop CheckSum
>
> comments in line
>
> Regards,
> Liang
> ________________________________________
> 发件人: Jean-Marc Spaggiari [jean-marc@spaggiari.org]
> 发送时间: 2013年2月26日 20:03
> 收件人: user
> 主题: HBase CheckSum vs Hadoop CheckSum
>
> Hi,
>
> 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);
>
>
> Thanks,
>
> JM

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