Compression in backups and restores
If you compress your data before a backup or unload procedure, you can improve its performance. Less data travels through the fabric and less data is written to disk, which saves space on the storage device. However, the compression process itself takes some time, so typically the larger the table the greater the benefit from compression.
A compressed binary format external table (also known as an internal format table) is a proprietary format, which typically yields smaller data files, retains information about the system topology, and thus is often faster to back up and restore. The alternative to compressed binary format is text format, which is a nonproprietary external table format that is independent of the Netezza Performance Server topology, but yields larger files and can be slower to back up and restore.
- When you use the standard backup by using the nzbackup and nzrestore commands, the system automatically uses compressed external tables as the data transfer mechanism.
- When you use compressed external table unload, the system compresses the data and only
decompresses it when you reload the data.
Use manually created external compressed tables for backup when you want table-level backup or the ability to send data to a named pipe. For example, when you use a named pipe with a third-party backup application.
- When you use text format unload, the data is not compressed. For large tables, it is the slowest method and the one that takes up the most storage space.