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From Jean-Marc Spaggiari <jean-m...@spaggiari.org>
Subject Re: CheckPoint Node
Date Sat, 01 Dec 2012 02:25:23 GMT
Sorry about that. My fault.

I have put this on the core-site.xml file but should be on the hdfs-site.xml...

I moved it and it's now working fine.

Thanks.

JM

2012/11/30, Jean-Marc Spaggiari <jean-marc@spaggiari.org>:
> 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 <jean-marc@spaggiari.org>:
>> 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 <harsh@cloudera.com>:
>>> 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
>>> <jean-marc@spaggiari.org> 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 <harsh@cloudera.com>:
>>>>> 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
>>>>> this since it is now available), the presence of > 1 NameNodes and
the
>>>>> journal log mount or quorum setup would automatically act as
>>>>> safeguards for the FS metadata.
>>>>>
>>>>> On Thu, Nov 22, 2012 at 11:03 PM, Jean-Marc Spaggiari
>>>>> <jean-marc@spaggiari.org> wrote:
>>>>>> Hi Harsh,
>>>>>>
>>>>>> Thanks for pointing me to this link. I will take a close look at
it.
>>>>>>
>>>>>> So with 1.x and 0.23.x, what's the impact on the data if the namenode
>>>>>> server hard-drive die? Is there any critical data stored locally?
Or
>>>>>> I
>>>>>> simply need to build a new namenode, start it and restart all my
>>>>>> namenodes to find my data back?
>>>>>>
>>>>>> I can deal with my application not beeing available, but loosing
data
>>>>>> can be a bigger issue.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> JM
>>>>>>
>>>>>> 2012/11/22, Harsh J <harsh@cloudera.com>:
>>>>>>> Hey Jean,
>>>>>>>
>>>>>>> The 1.x, 0.23.x release lines both don't have NameNode HA features.
>>>>>>> The current 2.x releases carry HA-NN abilities, and this is
>>>>>>> documented
>>>>>>> at
>>>>>>> http://hadoop.apache.org/docs/current/hadoop-yarn/hadoop-yarn-site/HDFSHighAvailability.html.
>>>>>>>
>>>>>>> On Thu, Nov 22, 2012 at 10:18 PM, Jean-Marc Spaggiari
>>>>>>> <jean-marc@spaggiari.org> wrote:
>>>>>>>> Replying to myself ;)
>>>>>>>>
>>>>>>>> By digging a bit more I figured that 1.0 version is older
than
>>>>>>>> 0.23.4
>>>>>>>> version and that backupnodes are on 0.23.4. Secondarynamenodes
on
>>>>>>>> 1.0
>>>>>>>> are now deprecated.
>>>>>>>>
>>>>>>>> I'm still a bit mixed up on the way to achieve HA for the
namenode
>>>>>>>> (1.0 or 0.23.4) but I will continue to dig over internet.
>>>>>>>>
>>>>>>>> JM
>>>>>>>>
>>>>>>>> 2012/11/22, Jean-Marc Spaggiari <jean-marc@spaggiari.org>:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> I'm reading a bit about hadoop and I'm trying to increase
the HA
>>>>>>>>> of
>>>>>>>>> my
>>>>>>>>> current cluster.
>>>>>>>>>
>>>>>>>>> Today I have 8 datanodes and one namenode.
>>>>>>>>>
>>>>>>>>> By reading here: http://www.aosabook.org/en/hdfs.html
I can see
>>>>>>>>> that
>>>>>>>>> a
>>>>>>>>> Checkpoint node might be a good idea.
>>>>>>>>>
>>>>>>>>> So I'm trying to start a checkpoint node. I looked at
the hadoop
>>>>>>>>> online doc. There is a link toe describe the command
usage "For
>>>>>>>>> command usage, see namenode." but this link is not working.
Also,
>>>>>>>>> if
>>>>>>>>> I
>>>>>>>>> try hadoop-deamon.sh start namenode -checkpoint as discribed
in
>>>>>>>>> the
>>>>>>>>> documentation, it's not starting.
>>>>>>>>>
>>>>>>>>> So I'n wondering, is there anywhere where I can find
up to date
>>>>>>>>> documentation about the checkpoint node? I will most
probably try
>>>>>>>>> the
>>>>>>>>> BackupNode.
>>>>>>>>>
>>>>>>>>> I'm using hadoop 1.0.3. The options I have to start on
this
>>>>>>>>> version
>>>>>>>>> are namenode, secondarynamenode, datanode, dfsadmin,
mradmin, fsck
>>>>>>>>> and
>>>>>>>>> fs. Should I start some secondarynamenodes instead of
backupnode
>>>>>>>>> and
>>>>>>>>> checkpointnode?
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>>
>>>>>>>>> JM
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Harsh J
>>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Harsh J
>>>>>
>>>
>>>
>>>
>>> --
>>> Harsh J
>>>
>>
>

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