1)      Is it possible to do an "in-place" migration, while keeping all
data in HDFS safely?

yes. stop the HDFS firstly, then run "start-dfs.sh -upgrade"

2)      If it is yes, is there any doc/guidance to do this?

you just want a HDFS upgrade, so I don't think there are some useful doc.

3)      Is the 2.0.3 MR API binary compatible with the one of 1.0.1?

Not much compatible of the FileSystem API. and there are some new HDFS
configurations and some depracates.
On Thu, Mar 6, 2014 at 12:47 PM, Jerry Zhang <[EMAIL PROTECTED]> wrote:
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