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 >
