oh, got it. you are a good guy. --Send from my Sony mobile. On Apr 7, 2013 10:11 PM, "Harsh J" <[email protected]> wrote:
> StandbyNameNode is the term we use to refer to a NameNode in HA that > is currently not the active one (i.e. its state is 'Standby'). Its not > a special type of daemon (i.e. it just runs the NameNode service), > just a naming convention. > > On Sun, Apr 7, 2013 at 7:31 PM, Azuryy Yu <[email protected]> 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" <[email protected]> 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 <[email protected]> wrote: > >> > Hi Harsh, > >> > Do you mean BackupNameNode is Secondary NameNode in Hadoop1.x? > >> > > >> > > >> > On Sun, Apr 7, 2013 at 4:05 PM, Harsh J <[email protected]> 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 <[email protected]> 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 <[email protected]> > wrote: > >> >> >> > >> >> >> Hi Lin, > >> >> >> > >> >> >> My reply inline. > >> >> >> > >> >> >> On Sun, Apr 7, 2013 at 12:36 PM, Lin Ma <[email protected]> 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 > > > > -- > Harsh J >
