SQL 2008 Backups: Compression Comparison and Notes

Here’s a transact-SQL to show you a comparison of a compressed and uncomopressed backup from your SQL server instance.
Backup compression is a new feature in SQL Server 2008 that can help provide smaller sized backups and reduce backup time.
(Reference)

SELECT
  b.database_name 'Database Name',
  CONVERT (BIGINT, b.backup_size / 1048576 ) 'UnCompressed Backup Size (MB)',
  CONVERT (BIGINT, b.compressed_backup_size / 1048576 ) 'Compressed Backup Size (MB)',
  CONVERT (NUMERIC (20,2), (CONVERT (FLOAT, b.backup_size) /
  CONVERT (FLOAT, b.compressed_backup_size))) 'Compression Ratio',
  DATEDIFF (SECOND, b.backup_start_date, b.backup_finish_date) 'Backup Elapsed Time (sec)'
FROM
  msdb.dbo.backupset b
WHERE
  DATEDIFF (SECOND, b.backup_start_date, b.backup_finish_date) > 0
  AND b.backup_size > 0
ORDER BY
  b.backup_finish_date DESC

You can also find out compression ratio with this transact-SQL code (Reference):

SELECT backup_size/compressed_backup_size FROM msdb..backupset;

Determine if you have backup compression enabled on a database:

USE AdventureWorks2012 ;
GO
SELECT value
FROM sys.configurations
WHERE name = 'backup compression default' ;
GO

Configure backup compression and enable it on a database:

USE AdventureWorks2012;
GO
EXEC sp_configure 'backup compression default', 1 ;
RECONFIGURE WITH OVERRIDE ;
GO

Alternatively, you can use the WITH NO_COMPRESSION or WITH COMPRESSION in your BACKUP statement to override the database default.