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Sanjay Radia commented on HDFS-3225: ------------------------------------ HDFS's upgrade snapshot feature is a unique and powerful part upgrading HDFS across versions. An HDFS upgrade involves snapshots of the data on NN and DNs. Upgrade Snapshots are not just for layout changes but also for data protection against a version change that introduces a bug that wipes out a portion or all of the data. (Other systems ask the admin to do a backup before starting the upgrade - that does not make sense for HDFS). For example, Yahoo does snapshot as part of all upgrades, except for minor fixes such as Emergency-Bug-Fixes. We need to revisit upgrade snapshots in light of rolling upgrades. > Revist upgrade snapshots, roll back, finalize to enable rolling upgrades > ------------------------------------------------------------------------ > > Key: HDFS-3225 > URL: https://issues.apache.org/jira/browse/HDFS-3225 > Project: Hadoop HDFS > Issue Type: New Feature > Reporter: Sanjay Radia > -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira