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From Uma Maheswara Rao G 72686 <mahesw...@huawei.com>
Subject Re: Secondary namenode fsimage concept
Date Tue, 11 Oct 2011 02:46:34 GMT
Hi,

It looks to me that, problem with your NFS. It is not supporting locks. Which version of NFS
are you using? 
Please check your NFS locking support by writing simple program for file locking.

I think NFS4 supports locking ( i did not tried).

http://nfs.sourceforge.net/

  A6. What are the main new features in version 4 of the NFS protocol?
  *NFS Versions 2 and 3 are stateless protocols, but NFS Version 4 introduces state. An NFS
Version 4 client uses state to notify an NFS Version 4 server of its intentions on a file:
locking, reading, writing, and so on. An NFS Version 4 server can return information to a
client about what other clients have intentions on a file to allow a client to cache file
data more aggressively via delegation. To help keep state consistent, more sophisticated client
and server reboot recovery mechanisms are built in to the NFS Version 4 protocol.
 *NFS Version 4 introduces support for byte-range locking and share reservation. Locking in
NFS Version 4 is lease-based, so an NFS Version 4 client must maintain contact with an NFS
Version 4 server to continue extending its open and lock leases. 


Regards,
Uma
----- Original Message -----
From: Shouguo Li <the1plummie@gmail.com>
Date: Tuesday, October 11, 2011 2:31 am
Subject: Re: Secondary namenode fsimage concept
To: common-user@hadoop.apache.org

> hey parick
> 
> i wanted to configure my cluster to write namenode metadata to 
> multipledirectories as well:
>  <property>
>    <name>dfs.name.dir</name>
>    <value>/hadoop/var/name,/mnt/hadoop/var/name</value>
>  </property>
> 
> in my case, /hadoop/var/name is local directory, 
> /mnt/hadoop/var/name is NFS
> volume. i took down the cluster first, then copied over files from
> /hadoop/var/name to /mnt/hadoop/var/name, and then tried to start 
> up the
> cluster. but the cluster won't start up properly...
> here's the namenode log: http://pastebin.com/gmu0B7yd
> 
> any ideas why it wouldn't start up?
> thx
> 
> 
> On Thu, Oct 6, 2011 at 6:58 PM, patrick sang 
> <silvianhadoop@gmail.com>wrote:
> > I would say your namenode write metadata in local fs (where your 
> secondary> namenode will pull files), and NFS mount.
> >
> >  <property>
> >    <name>dfs.name.dir</name>
> >    <value>/hadoop/name,/hadoop/nfs_server_name</value>
> >  </property>
> >
> >
> > my 0.02$
> > P
> >
> > On Thu, Oct 6, 2011 at 12:04 AM, shanmuganathan.r <
> > shanmuganathan.r@zohocorp.com> wrote:
> >
> > > Hi Kai,
> > >
> > >      There is no datas stored  in the secondarynamenode related 
> to the
> > > Hadoop cluster . Am I correct?
> > > If it correct means If we run the secondaryname node in 
> separate machine
> > > then fetching , merging and transferring time is increased if 
> the cluster
> > > has large data in the namenode fsimage file . At the time if 
> fail over
> > > occurs , then how can we recover the nearly one hour changes in 
> the HDFS
> > > file ? (default check point time is one hour)
> > >
> > > Thanks R.Shanmuganathan
> > >
> > >
> > >
> > >
> > >
> > >
> > > ---- On Thu, 06 Oct 2011 12:20:28 +0530 Kai Voigt<k@123.org&gt; 
> wrote> > ----
> > >
> > >
> > > Hi,
> > >
> > > the secondary namenode only fetches the two files when a 
> checkpointing is
> > > needed.
> > >
> > > Kai
> > >
> > > Am 06.10.2011 um 08:45 schrieb shanmuganathan.r:
> > >
> > > &gt; Hi Kai,
> > > &gt;
> > > &gt; In the Second part I meant
> > > &gt;
> > > &gt;
> > > &gt; Is the secondary namenode also contain the FSImage file or 
> the two
> > > files(FSImage and EdiltLog) are transferred from the namenode 
> at the
> > > checkpoint time.
> > > &gt;
> > > &gt;
> > > &gt; Thanks
> > > &gt; Shanmuganathan
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt; ---- On Thu, 06 Oct 2011 11:37:50 +0530 Kai 
> Voigt&amp;lt;k@123.org> &amp;gt;
> > > wrote ----
> > > &gt;
> > > &gt;
> > > &gt; Hi,
> > > &gt;
> > > &gt; you're correct when saying the namenode hosts the fsimage 
> file and
> > the
> > > edits log file.
> > > &gt;
> > > &gt; The fsimage file contains a snapshot of the HDFS metadata (a
> > filename
> > > to blocks list mapping). Whenever there is a change to HDFS, it 
> will be
> > > appended to the edits file. Think of it as a database 
> transaction log,
> > where
> > > changes will not be applied to the datafile, but appended to a 
> log.> > &gt;
> > > &gt; To prevent the edits file growing infinitely, the 
> secondary namenode
> > > periodically pulls these two files, and the namenode starts 
> writing> changes
> > > to a new edits file. Then, the secondary namenode merges the 
> changes from
> > > the edits file with the old snapshot from the fsimage file and 
> creates an
> > > updated fsimage file. This updated fsimage file is then copied 
> to the
> > > namenode.
> > > &gt;
> > > &gt; Then, the entire cycle starts again. To answer your 
> question: The
> > > namenode has both files, even if the secondary namenode is 
> running on a
> > > different machine.
> > > &gt;
> > > &gt; Kai
> > > &gt;
> > > &gt; Am 06.10.2011 um 07:57 schrieb shanmuganathan.r:
> > > &gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt; Hi All,
> > > &gt; &amp;gt;
> > > &gt; &amp;gt; I have a doubt in hadoop secondary namenode 
> concept .
> > Please
> > > correct if the following statements are wrong .
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt; The namenode hosts the fsimage and edit log 
> files. The
> > > secondary namenode hosts the fsimage file only. At the time of 
> checkpoint> > the edit log file is transferred to the secondary 
> namenode and the both
> > > files are merged, Then the updated fsimage file is transferred 
> to the
> > > namenode . Is it correct?
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt; If we run the secondary namenode in separate 
> machine , then
> > > both machines contain the fsimage file . Namenode only contains 
> the> editlog
> > > file. Is it true?
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt; Thanks R.Shanmuganathan
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt; &amp;gt;
> > > &gt;
> > > &gt; --
> > > &gt; Kai Voigt
> > > &gt; k@123.org
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt;
> > > &gt;
> > >
> > > --
> > > Kai Voigt
> > > k@123.org
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> 

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