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Re: backup node question
Azuryy Yu 2013-04-07, 14:02
SNN=secondary name node  in my last mail.

--Send from my Sony mobile.
On Apr 7, 2013 10:01 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
>>
>