Difference between Mirrored and Striped Database Backups in SQL Server

Mirrored Database Backup:

A Mirrored Database Backup (supported in SQL Server 2005 Enterprise Edition and later versions) is a database backup where a database backup file is written to two or more (maximum 4) different locations simultaneously. To successfully make a mirrored backup, all the defined mirrors must be present. To restore a backup from a mirrored media set, you can specify any single mirror location.

Make sure that you have the specified backup folders created before you start backup operation. If the specified folders are not created before you start backup operation, you will get the following error:

Msg 3201, Level 16, State 1, Line 1
Cannot open backup device 'D:\Backup\AdventureWorks1.bak'. Operating system error 3(The system cannot find the path specified.).
Msg 3013, Level 16, State 1, Line 1
BACKUP DATABASE is terminating abnormally.

You cannot do a mirrored backup from a SQL Server Management Studio "Back Up Database" dialog box (it can be used for striped backups).
Here is a script for a single file Mirrored Database Backup:

BACKUP DATABASE [AdventureWorks]
TO DISK = N'C:\Backup\AdventureWorks.bak'
MIRROR TO DISK = N'D:\Backup\AdventureWorks.bak'
WITH FORMAT;
GO

mirrored_backup_format

The first time you run this command, you will have to use the WITH FORMAT clause to overwrite any existing backups and create a new media set.
If you run the command using WITH NOFORMAT clause the first time you run this command, you will get the following error:

Msg 3215, Level 16, State 1, Line 1
Use WITH FORMAT to create a new mirrored backup set.
Msg 3013, Level 16, State 1, Line 1
BACKUP DATABASE is terminating abnormally.

mirrored_backup_noformat_error

Later, when a new media set is created, you can use WITH NOFORMAT clause.

Striped Database Backup (Split File Backup):

Striped Database Backup (Split File Backup) is a database backup where a single backup file is split into multiple files that are simultaneously written to different locations. It is usually used to increase backup performance and speed or to distribute space usage across different disks. All striped backup files are needed to restore the database.

Here is a script for Striped Database Backup:

BACKUP DATABASE [AdventureWorks]
TO DISK = N'C:\Backup\AdventureWorks.bak',
DISK = N'D:\Backup\AdventureWorks.bak'
WITH NOFORMAT;
GO

Striped Database Backup can be done using a SQL Server Management Studio "Back Up Database" dialog box:

Right click on a database -> choose 'Tasks' -> 'Back Up...'
In the "Back Up Database" dialog box, type the locations and backup file names (all the files will be needed for the database restore):

back_up_striped_ssms

To see how to Restore a SQL Server Database from Striped Backup Files, read related blog post:
Restore a SQL Server Database from Striped Backup Files

Striped Database Backup to Multiple Locations using Mirror:

SQL Server Mirrored Database Backup supports backup of the Striped (Split) Backup files:

BACKUP DATABASE [AdventureWorks]
TO DISK = N'C:\Backup\AdventureWorks1.bak',
DISK = N'C:\Backup\AdventureWorks2.bak'
MIRROR TO DISK = N'D:\Backup\AdventureWorks1.bak',
DISK = N'D:\Backup\AdventureWorks2.bak'
WITH FORMAT;
GO

mirrored_striped_backup_format

It is necessary that all mirrors have the same number of members, or you will get the following error:

Msg 3010, Level 16, State 1, Line 1
Invalid backup mirror specification. All mirrors must have the same number of members.

mirrored_striped_backup_error_3010