Symptoms
A database, log, file or file group backup, which was backed up to multiple tape backup devices (otherwise known as a striped dump), may fail to restore if fewer devices are used on the RESTORE operation than were used on the BACKUP. An extra tape mount is requested that can never be satisfied.
Note that this problem occurs with either the native SQL Server RESTORE command, or with the Original Equipment Manufacturer (OEM) backup/restore solutions that utilize the SQL Server Virtual Backup Device Interface (VDI) API.
Resolution
Restore using either a single backup device, or the same number of devices used to create the striped backup.