Yes, if there are missing blocks (i.e. all replicas lost), and the block availability threshold is set to its default of 0.999f (99.9% availability required), then NN will not come out of safemode automatically. You can control this behavior by configuring dfs.namenode.safemode.threshold.
On Wed, Jan 30, 2013 at 10:06 PM, Chen He <airb...@gmail.com> 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 <ha...@cloudera.com> 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 <zhunans...@gmail.com> 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 > > -- Harsh J