Hello! I am trying to perform a rolling upgrade of a cluster running hadoop-2.4.1 without downtime following procedure described at http://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/HdfsRollingUpgrade.html
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!
