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From Mingliang Liu <lium...@apache.org>
Subject Re: Safe mode on after restarting hadoop
Date Thu, 22 Dec 2016 18:39:51 GMT
Anu gave good analysis. Another simple case is that NN takes time to process the block reports
before leaving the safe mode. You can monitor the safe mode report for progress. Check NN
log for more information.


> On Dec 22, 2016, at 8:02 AM, Chathuri Wimalasena <kamalasini@gmail.com> wrote:
> Hi, 
> We have a hadoop cluster with 10 data nodes. We had a disk failure with the login node
where the namenode, secondary namenode running and replaced the failed disk. Failed disk does
not affect the data, it only affected the operating system. After replacing the failed disk,
when I restart the hadoop services, hadoop is set to safe mode and does not let run jobs.
Below message shows in namenode UI.
> Safe mode is ON. The reported blocks 391253 needs additional 412776 blocks to reach the
threshold 0.9990 of total blocks 804833. The number of live datanodes 10 has reached the minimum
number 0. Safe mode will be turned off automatically once the thresholds have been reached.
> I can see all the data nodes are up and running. Also when I check for corrupt blocks,
it shows as 0.
> hdfs fsck / -list-corruptfileblocks
> Connecting to namenode via http://ln02:50070/fsck?ugi=hadoop&listcorruptfileblocks=1&path=%2F
> The filesystem under path '/' has 0 CORRUPT files
> Any idea what's going on ? I can forcefully leave the safemode, but I'm worried whether
it might cause data corruption. Are there any safety steps I should do before leave the safemode
forcefully ?
> Thanks,
> Chathuri

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