Upgrade not finalized

[Ulrich Kammer]

Hello,

in april we have upgraded our version of Hadoop 0.21.0 to version 1.0.1. 
We stuck to the exact instructions in the upgrade documentation as 
always. After a few months we have discovered on the Namenode that here 
again "upgrade for version -32 has been completed. Upgrade is not 
finalized." is displayed. Our question now is, can we run this command 
without risk again? According to our research, this command deletes the 
directory on the Data Nodes "previous" and the directories on the 
namenode "previous" and "previous.checkpoint". It is very important that 
we here do not lose data. A backup is not possible for reasons of cost. 
Is there eventually an easy way to test it?

Ulrich