Compression Levels

SQL Backup Manager offers three compression levels, described below. Generally, the smaller the resulting backup file, the slower the backup process.

If you do not want to compress your backups, clear the Use data compression check box in the wizard. For example, you may want to do this if you require only encryption and you do not want to compress your backups.

Compression level - Fastest

This is the default compression level. It is the fastest compression, but results in larger backup files.

On average, the backup process is 10% to 20% faster than when compression level normal is used, and 20% to 33% fewer CPU cycles are used. Backup files are usually 5% to 9% larger than those produced by compression level normal.

However, if a database contains frequently repeated values, compression level fastest can produce backup files that are smaller than if you used compression level normal or maximal. For example, this may occur for a database that contains the results of Microsoft SQL Profiler trace sessions.

Compression level - Normal

This compression level uses the zlib compression algorithm, and is a variation of compression level maximal.

On average, the backup process is 15% to 25% faster than when compression level maximal is used, and 12% to 14% fewer CPU cycles are used. Backup files are usually 4% to 6% larger.

Compression level - Maximal

This compression level uses the zlib compression algorithm. This compression level generates the smallest backup files in most cases, but it uses the most CPU cycles and takes the longest to complete.

Compression percentage

SQL Backup Manager calculates the percentage compression of a backup by comparing the size of the SQL Backup Manager backup with the total database size.

For example, if a database comprises a 10 GB data file and a 2 GB transaction log file and SQL Backup Manager generates a full backup of the database to create a backup file that is 3 GB, the compression for this backup is calculated as 75%, [1-(3/12)]x100.