Looks like hardware issue
KB Article ID: 10993
Article Type: Troubleshooting
Published: 5/29/2007 2:48:13 PMWhile accessing a drive the Serial Number obtained is different from expected Serial Number
You encounter the one of the following errors during a backup, Aux Copy, or a restore operation:
While accessing a drive, the Serial Number obtained is different from expected Serial Number.
Failed to mount media with barcode , side , into drive , in library  on MediaAgent . Reason: While accessing a drive, the Serial Number obtained is different from expected Serial Number. Advice: There is a drive access path change. Please run SCSI Detection on the MediaAgents.
During the initial configuration of a library, the serial numbers of each of the drives being configured is recorded. Each time a tape is mounted to a drive, the serial number of the target drive is matched with the recorded value. To prevent data loss, Galaxy will only write to the drive if the serial numbers match. If the actual serial number differs from the recorded value, or if no serial number is returned, the above error is generated and the job will fail to proceed.
The most common reasons for a serial number mismatch include:
1. A drive has been replaced in your library.
2. A drive has had its Access path reassigned by the operating system.
3. A drive is no longer visible to or detected by the operating system.
Other causes may include faulty hardware or incorrect/corrupted drivers for the drives.
If you have had one or more of your drives replaced recently, this error is normal and indicates that the previous drive is no longer present. Please see the Additional Information section below for information on properly configuring your new drive.
In most cases either a basic or exhaustive detection will correct the library configuration and resolve this issue. Since an exhaustive detection can take a long time, our preference is to start with a basic detection.
Following the detection, resume the job. If the job fails with the same error attempt an exhaustive detection.
The steps for performing basic and exhaustive detect operations can be found in the Detect Devices Using Exhaustive Detection documentation page.
If you have replaced one or more of your drives recently, please configure your new drive as described in the documentation page Replacing a Drive with the Same Drive Type.
In the case of NDMP attached tape drives, you will need to contact the file server vendor for assistance. Each has their own process for recovering device connectivity, and CommVault cannot provide details in their behalf.
CommVault Certified Engineer