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MapReduce, mail # user - CheckPoint Node


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Jean-Marc Spaggiari 2012-11-22, 16:27
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Jean-Marc Spaggiari 2012-11-22, 16:48
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Harsh J 2012-11-22, 17:25
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Jean-Marc Spaggiari 2012-11-22, 17:33
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Harsh J 2012-11-22, 17:45
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Jean-Marc Spaggiari 2012-11-22, 18:29
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Harsh J 2012-11-22, 18:42
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Jean-Marc Spaggiari 2012-11-22, 19:09
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Re: CheckPoint Node
Jean-Marc Spaggiari 2012-12-01, 02:11
Hi,

Is there a way to ask Hadoop to display its parameters?

I have updated the property as followed:
  <property>
    <name>dfs.name.dir</name>
    <value>${hadoop.tmp.dir}/dfs/name,/media/usb0/</value>
  </property>

But even if I stop/start hadoop, there is nothing written on the usb
drive. So I'm wondering if there is a command line like bin/hadoop
--showparameters

Thanks,

JM

2012/11/22, Jean-Marc Spaggiari <[EMAIL PROTECTED]>:
> Perfect. Thanks again for your time!
>
> I will first add another drive on the Namenode because this will take
> 5 minutes. Then I will read about the migration from 1.0.3 to 2.0.x
> and most probably will use the zookeeper solution.
>
> This will take more time, so will be done over the week-end.
>
> I lost 2 hard drives this week (2 datanodes), so I'm not a bit
> concerned about the NameNode data. Just want to secure that a bit
> more.
>
> JM
>
> 2012/11/22, Harsh J <[EMAIL PROTECTED]>:
>> Jean-Marc (Sorry if I've been spelling your name wrong),
>>
>> 0.94 does support Hadoop-2 already, and works pretty well with it, if
>> that is your only concern. You only need to use the right download (or
>> if you compile, use the -Dhadoop.profile=23 maven option).
>>
>> You will need to restart the NameNode to make changes to the
>> dfs.name.dir property and set it into effect. A reasonably fast disk
>> is needed for quicker edit log writes (few bytes worth in each round)
>> but a large, or SSD-style disk is not a requisite. An external disk
>> would work fine too (instead of an NFS), as long as it is reliable.
>>
>> You do not need to copy data manually - just ensure that your NameNode
>> process user owns the directory and it will auto-populate the empty
>> directory on startup.
>>
>> Operationally speaking, in case 1/2 disk fails, the NN Web UI (and
>> metrics as well) will indicate this (see bottom of NN UI page for an
>> example of what am talking about) but the NN will continue to run with
>> the lone remaining disk, but its not a good idea to let it run for too
>> long without fixing/replacing the disk, for you will be losing out on
>> redundancy.
>>
>> On Thu, Nov 22, 2012 at 11:59 PM, Jean-Marc Spaggiari
>> <[EMAIL PROTECTED]> wrote:
>>> Hi Harsh,
>>>
>>> Again, thanks a lot for all those details.
>>>
>>> I read the previous link and I totally understand the HA NameNode. I
>>> already have a zookeeper quorum (3 servers) that I will be able to
>>> re-use. However, I'm running HBase 0.94.2 which is not yet compatible
>>> (I think) with Hadoop 2.0.x. So I will have to go with a non-HA
>>> NameNode until I can migrate to a stable 0.96 HBase version.
>>>
>>> Can I "simply" add one directory to dfs.name.dir and restart
>>> my namenode? Is it going to feed all the required information in this
>>> directory? Or do I need to copy the data of the existing one in the
>>> new one before I restart it? Also, does it need a fast transfert rate?
>>> Or will an exteral hard drive (quick to be moved to another server if
>>> required) be enought?
>>>
>>>
>>> 2012/11/22, Harsh J <[EMAIL PROTECTED]>:
>>>> Please follow the tips provided at
>>>> http://wiki.apache.org/hadoop/FAQ#How_do_I_set_up_a_hadoop_node_to_use_multiple_volumes.3Fand
>>>> http://wiki.apache.org/hadoop/FAQ#If_the_NameNode_loses_its_only_copy_of_the_fsimage_file.2C_can_the_file_system_be_recovered_from_the_DataNodes.3F
>>>>
>>>> In short, if you use a non-HA NameNode setup:
>>>>
>>>> - Yes the NN is a very vital persistence point in running HDFS and its
>>>> data should be redundantly stored for safety.
>>>> - You should, in production, configure your NameNode's image and edits
>>>> disk (dfs.name.dir in 1.x+, or dfs.namenode.name.dir in 0.23+/2.x+) to
>>>> be a dedicated one with adequate free space for gradual growth, and
>>>> should configure multiple disks (with one off-machine NFS point highly
>>>> recommended for easy recovery) for adequate redundancy.
>>>>
>>>> If you instead use a HA NameNode setup (I'd highly recommend doing
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Jean-Marc Spaggiari 2012-12-01, 02:25
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Harsh J 2012-12-01, 04:24
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ac@...) 2012-12-01, 04:11