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From Dmitry Sivachenko <trtrmi...@gmail.com>
Subject rolling upgrade without downtime
Date Wed, 02 Sep 2015 09:43:52 GMT

I am trying to perform a rolling upgrade of a cluster running hadoop-2.4.1 without downtime
following procedure described at

The first command to execute is:

% hdfs dfsadmin -rollingUpgrade prepare
PREPARE rolling upgrade ...
rollingUpgrade: Safe mode should be turned ON in order to create namespace image.

So according to this message I must switch HDFS to safe mode first.

1) The documentation should be adjusted to mention that fact;
2) switching to safe mode will imply some restrictions to using the cluster, so it is not
*without downtime*

Or may be I am missing something?

Thanks in advance!
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