Hi Yogesh Just treat SecondaryName Node as a check pointing node. Name recovery is mostly done by writing the fsimage and edit log to a remote nfs mount other than the local fs. So that if the copy on local disk gets corrupted or lost on a disk failure or machine failure the one from remote mount can be used.
You can read more here http://wiki.apache.org/hadoop/NameNodeFailover Regards Bejoy KS On Fri, Jul 20, 2012 at 3:58 PM, <yogesh.kuma...@wipro.com> wrote: > Thanks Mohammad :-), > > I just read this concept of secondary NameNode. Thank you for your reply. > Mohammad I am not finding the way to implement would you please explain me > regarding to recover namenode, Iam getting confuse. > > Thanks & Regards > Yogesh Kumar Dhari > > ________________________________________ > From: Mohammad Tariq [donta...@gmail.com] > Sent: Friday, July 20, 2012 3:17 PM > To: hdfs-user@hadoop.apache.org > Subject: Re: NameNode fails > > Hi yogesh, > > First of all, we should always keep it mind that Secondary > Namenode is not a backup for the Namenode. By its name, it gives a > sense that its a backup for the Namenode, but in reality its not. > Namenode stores data in 2 files : > 1- fsimage - snapshot of the filesystem when namenode started > 2- Edit logs - contain the sequence of changes made to the filesystem > after namenode started. > > The sole purpose of Secondary Namenode is to have a checkpoint in HDFS > and it acts as a helper of the Namenode. It basically : > 1- gets the edit logs from the namenode in regular intervals and > applies to fsimage > 2- once it has new fsimage, it copies back to namenode > > Namenode uses this fsimage for the next restart. > > Regards, > Mohammad Tariq > > > On Fri, Jul 20, 2012 at 1:59 PM, <yogesh.kuma...@wipro.com> wrote: >> Hi Bejoy, >> >> Its done now, Error log was showing namenode is not formated, >> I closed all previous terminal and restarted it after formatting. >> >> its running now. >> >> Please suggest me that if in case it gets crashed then how do I recover it >> from Secondary Namenode. how should I proceed for that >> >> >> Thanks & regards >> Yogesh Kumar Dhari >> ________________________________ >> From: Bejoy KS [bejoy.had...@gmail.com] >> Sent: Friday, July 20, 2012 12:56 PM >> To: Yogesh Kumar (WT01 - Communication and Media); >> hdfs-user@hadoop.apache.org >> Subject: Re: NameNode fails >> >> Hi Yogesh >> >> Please post in the error logs/messages if you find any. >> >> Regards >> Bejoy KS >> >> Sent from handheld, please excuse typos. >> ________________________________ >> From: <yogesh.kuma...@wipro.com> >> Date: Fri, 20 Jul 2012 07:21:24 +0000 >> To: <hdfs-user@hadoop.apache.org>; <bejoy.had...@gmail.com> >> Subject: RE: NameNode fails >> >> Thanks Bejoy, Mohammad and Vignesh :-). >> >> I have done the suggested by you and made thses changes. and formatted the >> namenode and trying to start cluster. >> but now name node is not starting :-( >> >> >> hdfs-site.xml >> >> ********************************************************** >> <configuration> >> <property> >> <name>dfs.replication</name> >> <value>1</value> >> </property> >> >> <property> >> <name>dfs.name.dir</name> >> <value>/HADOOP/hadoop-0.20.2/hadoop_name_dirr</value> >> </property> >> >> <property> >> <name>dfs.data.dir</name> >> <value>/HADOOP/hadoop-0.20.2/hadoop_data_dirr</value> >> </property> >> >> </configuration> >> >> ************************************************************** >> >> >> >> hdfs-core.xml >> >> ************************************************************** >> >> <configuration> >> <property> >> <name>fs.default.name</name> >> <value>hdfs://localhost:9000</value> >> </property> >> >> <property> >> <name>hadoop.tmp.dir</name> >> <value>/HADOOP/hadoop-0.20.2/hadoop_temp_dirr</value> >> <description>A base for other temporary directories.</description> >> </property> >> >> </configuration> >> >> ***************************************************************** >> >> Please suggest. >> >> Thanks & Regards >> Yogesh Kumar Dhari >> >> >> ________________________________ >> From: Mohammad Tariq [donta...@gmail.com] >> Sent: Friday, July 20, 2012 12:17 PM >> To: hdfs-user@hadoop.apache.org; bejoy.had...@gmail.com >> Subject: Re: NameNode fails >> >> Hi yogesh, >> Do as suggested by bejoy and add the hadoop.tmp.dir in your >> core-site.xml file.it's value defaults to the /tmp dir which gets emptied at >> each restart so all the data is lost... also add dfs.name.dir and >> dfs.data.dir properties into your hdfs-site.xml file to avoid the data loss. >> >> On Friday, July 20, 2012, Bejoy KS <bejoy.had...@gmail.com> wrote: >>> Hi Yogesh >>> >>> Is your dfs.name.dir pointing to /tmp dir? If so try changing that to any >>> other dir . The contents of /tmp may get wiped out on OS restarts. >>> Regards >>> Bejoy KS >>> >>> Sent from handheld, please excuse typos. >>> ________________________________ >>> From: <yogesh.kuma...@wipro.com> >>> Date: Fri, 20 Jul 2012 06:20:02 +0000 >>> To: <hdfs-user@hadoop.apache.org> >>> ReplyTo: hdfs-user@hadoop.apache.org >>> Subject: NameNode fails >>> Hello All :-), >>> >>> I am new to Hdfs. >>> >>> I have installed single node hdfs and started all nodes, every nodes gets >>> started and work fine. >>> But when I shutdown my system or Restart it, then i try to run all nodes >>> but Namenode doesn't start . >>> >>> to Start it i need to format the namenode and all data gets wash off :-(. >>> >>> Please help me and suggest me regarding this and how can I recover >>> namenode from secondary name node on single node setup >>> >>> >>> Thanks & Regards >>> Yogesh Kumar Dhari >>> >>> Please do not print this email unless it is absolutely necessary. >>> >>> The information contained in this electronic message and any attachments >>> to this message are intended for the exclusive use of the addressee(s) and >>> may contain proprietary, confidential or privileged information. If you are >>> not the intended recipient, you should not disseminate, distribute or copy >>> this e-mail. Please notify the sender immediately and destroy all copies of >>> this message and any attachments. >>> >>> WARNING: Computer viruses can be transmitted via email. The recipient >>> should check this email and any attachments for the presence of viruses. The >>> company accepts no liability for any damage caused by any virus transmitted >>> by this email. >>> >>> www.wipro.com >> >> -- >> Regards, >> Mohammad Tariq >> >> Please do not print this email unless it is absolutely necessary. >> >> The information contained in this electronic message and any attachments to >> this message are intended for the exclusive use of the addressee(s) and may >> contain proprietary, confidential or privileged information. If you are not >> the intended recipient, you should not disseminate, distribute or copy this >> e-mail. Please notify the sender immediately and destroy all copies of this >> message and any attachments. >> >> WARNING: Computer viruses can be transmitted via email. The recipient should >> check this email and any attachments for the presence of viruses. The >> company accepts no liability for any damage caused by any virus transmitted >> by this email. >> >> www.wipro.com >> >> Please do not print this email unless it is absolutely necessary. >> >> The information contained in this electronic message and any attachments to >> this message are intended for the exclusive use of the addressee(s) and may >> contain proprietary, confidential or privileged information. If you are not >> the intended recipient, you should not disseminate, distribute or copy this >> e-mail. Please notify the sender immediately and destroy all copies of this >> message and any attachments. >> >> WARNING: Computer viruses can be transmitted via email. The recipient should >> check this email and any attachments for the presence of viruses. The >> company accepts no liability for any damage caused by any virus transmitted >> by this email. >> >> www.wipro.com > > Please do not print this email unless it is absolutely necessary. > > The information contained in this electronic message and any attachments to > this message are intended for the exclusive use of the addressee(s) and may > contain proprietary, confidential or privileged information. If you are not > the intended recipient, you should not disseminate, distribute or copy this > e-mail. Please notify the sender immediately and destroy all copies of this > message and any attachments. > > WARNING: Computer viruses can be transmitted via email. The recipient should > check this email and any attachments for the presence of viruses. The company > accepts no liability for any damage caused by any virus transmitted by this > email. > > www.wipro.com
