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HDFS >> mail # user >> Hadoop HA


Makes it two, countless enough. It's not that I disagree that the gasket
between the keyboard and the chair (aka user) is a typical source of most of
the troubles ;)

Cos

On Sat, May 26, 2012 at 08:44AM, M. C. Srivas wrote:
> On Fri, May 25, 2012 at 8:03 AM, Konstantin Boudnik <[EMAIL PROTECTED]> wrote:
>
> > BTW, Srivas,
> >
> > I could find a single countless example of horror story of 'hadoop fs
> > -rmr' in
> > a form of hypothetical question (and not on this list ;)
> > http://is.gd/55KD1E
> >
> >
> Hi Cos,  accidentally deleting files is one of the most common user errors.
> Here's a real one from just last month
>
> http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-user/201204.mbox/%3CCAPwpkBvEx4OTUbf6mf8t43oOjZM%2BExUths7XNn3UidqsN3Y8hA%40mail.gmail.com%3E
>
>
> As Patrick says in the follow-up, the only way to recover in this situation
> is to shutdown the cluster:
>
> http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-user/201204.mbox/%3CCANS822ga1ivAPi2C9PJsyz6nZgft4msKkH%3Dyj06-i_V%2Bu1B1AA%40mail.gmail.com%3E
>
>
>
> In fact, the above procedure is well-known and well-documented.  Here's
> even an excerpt from Jason's book ProHadoop where he says "it is not
> uncommon for a user to accidentally delete large portions of the HDFS file
> system due to a program error or a command-line error ... best bet is to
> terminate the NN and 2-N immediately, and then shutdown the DNs as fast as
> possible"
>
> http://books.google.com/books?id=8DV-EzeKigQC&pg=PA122&lpg=PA122&dq=how+to+recover+deleted+files+%2B+hadoop&source=bl&ots=prgSMk1SHL&sig=LPJ0j5MFwJ3zUAcOrvR6FbiWQuQ&hl=en&sa=X&ei=UfXAT76HJuabiALbkdn8Bw&ved=0CLQBEOgBMAQ#v=onepage&q=how%20to%20recover%20deleted%20files%20%2B%20hadoop&f=false
>
>
>
> Just for the sake of full disclosure, of course.
>
> >
> > Enjoy,
> >  Cos
> >
> > On Tue, May 22, 2012 at 09:45PM, M. C. Srivas wrote:
> > > On Tue, May 22, 2012 at 12:08 AM, Martinus Martinus
> > > <[EMAIL PROTECTED]>wrote:
> > >
> > > > Hi Todd,
> > > >
> > > > Thanks for your answer. Is that will have the same capability as the
> > > > commercial M5 of MapR : http://www.mapr.com/products/why-mapr ?
> > > >
> > > > Thanks.
> > >
> > >
> > > Hi Martinus,   some major differences in HA between MapR's M5 and Apache
> > > Hadoop
> > >
> > > 1. with M5, any node become master at any time. It is a fully
> > active-active
> > > system. You can get create a fully bomb-proof cluster, such that in a
> > > 20-node cluster, you can configure to survive even if 19 of the 20 nodes
> > > are lost. With Apache, it is a 1-1 active-passive system.
> > >
> > > 2. M5 does not require a NFS filer in the backend. Apache Hadoop
> > requires a
> > > Netapp or similar NFS filer to assist in saving the NN data, even in its
> > HA
> > > configuration.  Note that for true HA, the Netapp or similar also will
> > need
> > > to be HA.
> > >
> > > 3. M5 has full HA for the Job-Tracker as well.
> > >
> > > Of course, HA is only a small part of the total business continuity
> > story.
> > >  Full recovery in the face of any kind of failures is critical:
> > >
> > > With M5:
> > >
> > > -  If there is a complete cluster crash and reboot (eg, a full
> > > power-failure of the entire cluster), M5 will recover in 5-10 minutes,
> > and
> > > submitted jobs will resume from where they were.
> > >
> > > - with snapshots, if you upgrade your software and it corrupts data, M5
> > > provides snapshots to help you recover. The number of times I've seen
> > > someone running  "hadoop fs -rmr /" accidentally and asking for help on
> > > this mailing list is beyond counting. With M5, it is completely
> > recoverable
> > >
> > > - full disaster-recovery across clusters by mirroring.
> > >
> > > Hope that clarifies some of the differences.
> > >
> > >
> > > >
> > > >
> > > > On Tue, May 22, 2012 at 2:26 PM, Todd Lipcon <[EMAIL PROTECTED]>
> > wrote:
> > > >
> > > >> Hi Martinus,
> > > >>
> > > >> Hadoop HA is available in Hadoop 2.0.0. This release is currently