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MapReduce, mail # user - what will happen when HDFS restarts but with some dead nodes


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Re: what will happen when HDFS restarts but with some dead nodes
Chen He 2013-01-30, 16:36
Hi Harsh

I have a question. How namenode gets out of safemode in condition of data
blocks lost, only administrator? Accordin to my experiences, the NN (0.21)
stayed in safemode about several days before I manually turn safemode off.
There were 2 blocks lost.

Chen

On Wed, Jan 30, 2013 at 10:27 AM, Harsh J <[EMAIL PROTECTED]> wrote:

> NN does recalculate new replication work to do due to unavailable
> replicas ("under-replication") when it starts and receives all block
> reports, but executes this only after out of safemode. When in
> safemode, across the HDFS services, no mutations are allowed.
>
> On Wed, Jan 30, 2013 at 8:34 AM, Nan Zhu <[EMAIL PROTECTED]> wrote:
> > Hi, all
> >
> > I'm wondering if HDFS is stopped, and some of the machines of the cluster
> > are moved,  some of the block replication are definitely lost for moving
> > machines
> >
> > when I restart the system, will the namenode recalculate the data
> > distribution?
> >
> > Best,
> >
> > --
> > Nan Zhu
> > School of Computer Science,
> > McGill University
> >
> >
>
>
>
> --
> Harsh J
>