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Hadoop, mail # user - Re: 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
Nitin Pawar 2013-01-30, 16:39
following are the configs it looks for . Unless Admin forces it to come out
of safenode, it respects below values

dfs.namenode.safemode.threshold-pct0.999fSpecifies the percentage of blocks
that should satisfy the minimal replication requirement defined by
dfs.namenode.replication.min. Values less than or equal to 0 mean not to
wait for any particular percentage of blocks before exiting safemode.
Values greater than 1 will make safe mode permanent.
dfs.namenode.safemode.min.datanodes0Specifies the number of datanodes that
must be considered alive before the name node exits safemode. Values less
than or equal to 0 mean not to take the number of live datanodes into
account when deciding whether to remain in safe mode during startup. Values
greater than the number of datanodes in the cluster will make safe mode
permanent.dfs.namenode.safemode.extension30000Determines extension of safe
mode in milliseconds after the threshold level is reached.
On Wed, Jan 30, 2013 at 10:06 PM, Chen He <[EMAIL PROTECTED]> wrote:

> 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
>>
>
>
--
Nitin Pawar