如何确保备份有效

备份时使用WITH CHECKSUM,如下所示，可以检查DB的Page是否有损坏。没有损坏就可以备份成功。

BACKUP DATABASE <DatabaseName> 
TO DISK= '<Backup_location>.bak' 
 WITH CHECKSUM 
GO 

如果损坏，则报如下信息，备份不成功：

Msg 824, Level 24, State 2, Line 1
SQL Server detected a logical consistency-based I/O error: incorrect checksum (expected: 0x9a3e399c; actual: 0x9a14b99c).
It occurred during a read of page (1:184) in database ID 23 at offset 0x00000000170000 in file
'D:\SQLDATA\ForcingFailures.mdf'. Additional messages in the SQL Server error log or system event log may provide more detail. This is a severe error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.BACKUP...WITH CHECKSUM is a useful tool and I recommend its use. Enabling checksums (and other checks, such as torn page detection) will bring with it only a small CPU overhead and should only have a minimal impact on the speed of your backups.

In addition, schedule regular consistency checks for each database, usingDBCC CHECKDB. Weekly checks are optimal, but on a server where the spare CPU and disk capacity are not readily available then monthly checks are better no checks. You could also restore databases from a server that cannot sustain weekly integrity checks to a secondary server to perform the maintenance there.

In addition, again, it's a great idea to perform some test restores. This may seem obvious, but there many DBAs simply assume that their backups are good and let them sit on the shelf. We don't need to restore every backup in the system to check its health, but doing random spot checks now and again is an easy way to gain peace of mind regarding future restores, and to hone the recovery strategy. Each week, choose a random database, and restore its last full backup. If that database is subject to differential and log backups as well, choose a point-in-time test restore that uses a full, differential and a few log backup files