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Date: Sun, 27 Jan 2013 18:56:17 -0800
Message-ID: 
 <CAGpTDNebdxLL2TrgSV6FKV_Xk_eVe1m71FP-+yv4gHUy6cXb3g@mail.gmail.com>
Subject: Re: Short-circuit reads
From: Jean-Daniel Cryans <jdcryans@apache.org>
To: user@hbase.apache.org
Content-Type: text/plain; charset=ISO-8859-1

It's in the region server metrics and also published through JMX.

J-D

On Sun, Jan 27, 2013 at 2:55 PM, Jean-Marc Spaggiari
<jean-marc@spaggiari.org> wrote:
> Hi J-D,
>
> In your presentation, where are you getting the
> hdfsBlocksLocalityIndex value? I'm not able to find it in my UI...
>
> Thanks,
>
> JM
>
> 2013/1/27, Jean-Daniel Cryans <jdcryans@apache.org>:
>> On Sun, Jan 27, 2013 at 2:38 PM, Jean-Marc Spaggiari
>> <jean-marc@spaggiari.org> wrote:
>>> Does this have a significant increase on HBase performances?
>>
>> Ted beats me to linking to my own presentation :P
>>
>>> And what
>>> are the "risks" associated with short-circuit activation (if any)? No
>>> risks of corrupting data?
>>
>> No, nothing, apart.
>>
>>>
>>> Can this be activated after tables are already populated?
>>
>> Not related at all, this is a region server configuration.
>>
>>>
>>> JM
>>>
>>> 2013/1/27, Ted <yuzhihong@gmail.com>:
>>>> For hbase internal checksum, it is not in hbase 0.92.x release.
>>>>
>>>> Please use 0.94.2 or newer release.
>>>>
>>>> Thanks
>>>>
>>>> On Jan 27, 2013, at 2:29 PM, David Koch <ogdude@googlemail.com> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> I read about "short circuit reads" in the HBase documentation's
>>>>> performance
>>>>> section[1] and was wondering what people's experiences were using this
>>>>> in
>>>>> a
>>>>> production setting.
>>>>>
>>>>> Also,
>>>>>
>>>>> 1. Since only one dedicated user can take advantage of the feature do
>>>>> you
>>>>> launch all jobs as this user?
>>>>> 2. Can dfs.client.read.shortcircuit be set to false for jobs wich are
>>>>> not
>>>>> launched by the short-circuit user in order to avoid exceptions? In
>>>>> other
>>>>> words - can this setting be overriden by the client configuration's
>>>>> hbase-site.xml?
>>>>> 3. In the same context, it is suggested to enable HBase internal
>>>>> checksums[2]. Is this a feature which can be enabled in HBase 0.92.1
>>>>> which
>>>>> is part of the Cloudera 4.1.x release?
>>>>>
>>>>> Thank you,
>>>>>
>>>>> /David
>>>>>
>>>>> [1] http://hbase.apache.org/book/perf.hdfs.html#ftn.d2145e7370
>>>>> [2] https://issues.apache.org/jira/browse/HBASE-5074
>>>>
>>