1> 即使数据库启用了页压缩或行压缩，压缩备份也可以有效减小备份的大小，压缩备份的压缩效率取决于表中的数据类型
2> 数据库压缩有利于降低备份时间（因为数据库变小）
3> 对已启用压缩的数据库进行压缩备份,CPU消耗会变得更高
原文：
Backup compression can result in additional disk space savings even on databases that contain ROW or PAGE compressed tables or indexes. The size of the compressed backup and the backup compression ratio depend upon the characteristics of the data in the database, and they can vary from the results shown in these examples.
Backup operations on databases that use ROW or PAGE compression will likely result in shorter backup times, because the smaller database size translates into less I/O.
CPU consumption during the backup operation for databases that use ROW or PAGE compression may be higher as a result of less I/O, which results in more CPU time for compression operations.