SNN=secondary name node in my last mail. --Send from my Sony mobile. On Apr 7, 2013 10:01 PM, "Azuryy Yu" <azury...@gmail.com> wrote:
> I am confused. Hadoopv2 has NN SNN DN JN(journal node), so whats > Standby Namenode? > > --Send from my Sony mobile. > On Apr 7, 2013 9:03 PM, "Harsh J" <ha...@cloudera.com> wrote: > >> BackupNameNode is not present in the maintenance 1.x releases, it is a >> feature added to a higher version; you can try it out in 2.x today if >> you wish to. >> >> On Sun, Apr 7, 2013 at 3:12 PM, Azuryy Yu <azury...@gmail.com> wrote: >> > Hi Harsh, >> > Do you mean BackupNameNode is Secondary NameNode in Hadoop1.x? >> > >> > >> > On Sun, Apr 7, 2013 at 4:05 PM, Harsh J <ha...@cloudera.com> wrote: >> >> >> >> Yes, it need not keep an edits (transactions) stream locally cause >> >> those are passed synchronously to the BackupNameNode, which persists >> >> it on its behalf. >> >> >> >> On Sun, Apr 7, 2013 at 1:21 PM, Lin Ma <lin...@gmail.com> wrote: >> >> > Thanks Harsh, >> >> > >> >> > For your comments, "What it means is that the NameNode need not store >> >> > anything locally", you mean Primary Name Node do not need to store >> >> > checkpoint/journal locally, and only need to keep memory image >> >> > up-to-date >> >> > for edits? >> >> > >> >> > regards, >> >> > Lin >> >> > >> >> > >> >> > On Sun, Apr 7, 2013 at 3:31 PM, Harsh J <ha...@cloudera.com> wrote: >> >> >> >> >> >> Hi Lin, >> >> >> >> >> >> My reply inline. >> >> >> >> >> >> On Sun, Apr 7, 2013 at 12:36 PM, Lin Ma <lin...@gmail.com> wrote: >> >> >> > Hi guys, >> >> >> > >> >> >> > I am reading from this paper to learn about backup nodes >> >> >> > (http://www.storageconference.org/2010/Papers/MSST/Shvachko.pdf), >> >> >> > >> >> >> > It is mentioned, "It contains all file system metadata information >> >> >> > except >> >> >> > for block locations. It can perform all operations of the regular >> >> >> > NameNode >> >> >> > that do not involve modification of the namespace or knowledge of >> >> >> > block >> >> >> > locations. ", what kinds of operations do not need knowledge of >> block >> >> >> > locations? >> >> >> >> >> >> Operations that do not involve data reads or writes would not >> require >> >> >> knowledge of block locations. Applying also the restriction of no >> >> >> namespace mutation, an example would be listing directories and >> >> >> looking up file information via FileStatus objects (perhaps the only >> >> >> examples - its like a safemode but no reads either). >> >> >> >> >> >> > It is also mentioned, "Use of a BackupNode provides the option of >> >> >> > running >> >> >> > the NameNode without persistent storage, delegating responsibility >> >> >> > for >> >> >> > the >> >> >> > namespace state persisting to the BackupNode.", what means >> "running >> >> >> > the >> >> >> > NameNode without persistent storage" and "delegating >> responsibility >> >> >> > for >> >> >> > the >> >> >> > namespace state persisting"? >> >> >> >> >> >> What it means is that the NameNode need not store anything locally, >> >> >> but can rely on the edits being stored at the BackupNameNode which >> >> >> would continuously be receiving it. When restarted, it can grab a >> >> >> current checkpoint from the BNN and boot up anywhere, since there's >> no >> >> >> local storage requirement. >> >> >> >> >> >> -- >> >> >> Harsh J >> >> > >> >> > >> >> >> >> >> >> >> >> -- >> >> Harsh J >> > >> > >> >> >> >> -- >> Harsh J >> >
