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Trafodion offline backup and restore operation are performed using HBase snapshot fetaurefeature. Snapshots are a light weight way to keep the current state of a table without copying the data. After making changes to a table or in case of recovery, restoring the snapshot gives the previous state of the table. More on snapshots can be found at: http://blog.cloudera.com/blog/2013/03/introduction-to-apache-hbase-snapshots/.
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- Trafodion needs to be completely down before starting offline backup
- Snapshots are taken for all the Trafodion tables using the HBase shell snapshot command.
- Trafodion is restarted. Regular activity can resume on these tables, but they will not be included in the backup.
- Snapshots are exported one by one to HDFS folder using the TrafExportSnapshot class. For small tables this uses HDFS file copy while for large tables MapReduce is to copy HFiles. The number of mappers can vary by table. It is determined is determined by table size of table and number of files to be copy copied for that table,
- If necessary, backup files can be archived or moved to a different cluster using hadoop distcp or other methods.
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