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Re: HBase Checksum
Hi Robert,

That's perfectly fine, it was my next question ;)
Anoop, I saw a 5% performance increase by activating HBase Checksum.
Can I disable it again to retry the baseline and see the difference?
Or now that it's there, it's to late?

Also, regarding BlockReaderLocal, I don't find that in my logs, but
after I have activated the shortcircuit, I saw a 41% performance
increase, so I'm almost sure it's working, but I don't know either how
 to check that.

What's the best way to see that on the logs? It's not display when
HBase is starting. Even not displayed when I'n doing major

I turned org.apache.hadoop.hdfs.BlockReaderLocal loglevel to debug and
still can't see anything. Not in the region server, and not in the

Also, to check with HDFS level logs whether the checksum meta file is
getting read to the DFS client, I'm not really sure how to acheive


2013/2/1, Robert Dyer <[EMAIL PROTECTED]>:
> Ok grepping the RS logs I see nothing with 'local' in any of them.  Thanks
> for that hint.
> For the test I was using, I know it is data local.  Every map task launched
> data local, and no regions were moving recently.
> I think I've hijacked this thread enough, I'll move my issues to another.
> ;-)
> On Thu, Jan 31, 2013 at 11:51 PM, Anoop Sam John <[EMAIL PROTECTED]>
> wrote:
>> Hi Robert
>>           When HDFS is doing the local short circuit read, it will use
>> BlockReaderLocal class for reading.  There should be some logs at the DFS
>> client side (RS) which tells abt creating new BlockReaderLocal .  If you
>> can see this then sure the local read is happening.
>> Also check DN log.  If local read happening, then you will not see  read
>> request related logs for the HFile at the DN side.
>> You check your no# of HFiles and names for checking the logs
>> Are you sure that when you tested, u have data locality? Region movements
>> across RSs can break the full data locality.
>> -Anoop-
>> ________________________________________
>> From: Robert Dyer [[EMAIL PROTECTED]]
>> Sent: Friday, February 01, 2013 11:10 AM
>> To: Hbase-User
>> Subject: Re: HBase Checksum
>> Not trying to hijack your thread here...
>> But can you verify via logs that the shortcircuit is working?  Because I
>> enabled shortcircuit but I sure didn't see any performance increase.
>> I haven't tried enabling hbase checksum yet but I'd like to be able to
>> verify that works too.
>> On Thu, Jan 31, 2013 at 9:55 PM, Anoop Sam John <[EMAIL PROTECTED]>
>> wrote:
>> > You can check with HDFS level logs whether the checksum meta file is
>> > getting read to the DFS client? In the HBase handled checksum, this
>> should
>> > not happen.
>> > Have you noticed any perf gain when you configure the HBase handled
>> > checksum option?
>> >
>> > -Anoop-
>> > ________________________________________
>> > From: Jean-Marc Spaggiari [[EMAIL PROTECTED]]
>> > Sent: Friday, February 01, 2013 4:16 AM
>> > To: user
>> > Subject: HBase Checksum
>> >
>> > Hi,
>> >
>> > I have activated shortcircuit and checksum and I would like to get a
>> > confirmation that it's working fine.
>> >
>> > So I have activated short circuit first and saw a 40% improvement of
>> > the MR rowcount job. So I guess it's working fine.
>> >
>> > Now, I'm configuring the checksum option, and I'm wondering how I can
>> > do to validate that it's taken into consideration and used, or not. Is
>> > there a way to see that?
>> >
>> > Thanks,
>> >
>> > JM
>> >
> --
> Robert Dyer