Tape drive dump files are necessary and helpful for drive/media problem analysis. It contains unexpected sense data from a tape drive when the problem encountered. That is to say, you need a drive dump file for further analysis when there is a problem when tape reading/writing.

Some tape driver generates dump files automatically when there is a problem occured, like ibm tape driver, LTFS etc..  Some of them are not, like linux mt-st driver.

Usually drive dump files are not big, only few MB, they look like this for LTO drives.

-rw-r--r-- 1 root root 7648084 Apr 20 12:40 00078B4xxx-10WT025021.a
-rw-r--r-- 1 root root 7684632 Apr 20 12:40 00078B4xxx-10WT025021.b
-rw-r--r-- 1 root root 14360998 Apr 20 12:40 00078B4xxx-10WT025021.blz
-rw-r--r-- 1 root root 1624 Apr 20 13:03 metro.log

Here is an example show you how to capture a drive dump file using ITDT(IBM Tape Diagnostics Tool).

Reproduce the problem

The first step is to stop a the problem point, or reporduce it if you can.

For example:

# /bin/mt -f /dev/nst9 seek 69766
# tar -b 8192 -C ./ -xf /dev/nst9 mybackup
tar: Unexpected EOF in archive
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now

As you can see there is problem when reading from tape, don't touch anything now, just do next step

Capture dump file for the drive

#cd ITDT
# ./itdt
Please wait for startup completion....  (Q to quit)

                                                                             
                                                                               
     IBM Tape Diagnostic Tool Standard Edition - Version:9.0.0.20150729        
                                                                               
                                                                               
     Diagnostic and Maintenance Functions:                                     
     [S] Scan for tape drives and enter Diagnostic/Maintenance Mode            
     [H] Help                                                                  
     [Q] Quit program                                                          
                                                                               
     Notes:                                                                    
     - During a test, user data on the cartridge will be erased!               
     - Make sure no other program is accessing the devices used by ITDT!       
     - A device scan may take several minutes in some cases!                   
                                                                               
                                                                               
     Expert Functions for known devices:                                       
     [U] Tapeutil                                                              
     [A] Add Device Manually                                                   
                                             
                                                                               
<[H] Help | [Q] Quit | Command > s                                   

Chose option s to scan drives                                                       

     Scan running...                                                                  

Then screen will look like this:

    IBM Tape Diagnostic Tool Standard Edition  - Device List                  
                                                                               
       Host Bus  ID   LUN  Model          Serial       Fware  Changer     [#]  
 +----+----+----+----+----+--------------+------------+------+------------+-+  
 | 0  | 1  | 0  | 0  | 0  | ULT3580-TD6  | 00078B3xxx | F9A0 | 78221170xxx| |  
 | 1  | 1  | 0  | 1  | 0  | ULT3580-TD6  | 00078B4xxx | F9A0 | 78221170xxx| |  
 | 2  | 1  | 0  | 2  | 0  | ULT3580-TD6  | 00078B3xxx | F9A0 | 78221170xxx| |  
 | 3  | 1  | 0  | 3  | 0  | ULT3580-TD5  | 00078A2xxx | F990 | 78221170xxx| |  
 | 4  | 1  | 0  | 3  | 1  | 03584L32     | 78221170xxx| F030 |            | |  
 | 5  | 1  | 0  | 4  | 0  | ULT3580-TD5  | 00078A2xxx | F990 | 78221170xxx| |  
 | 6  | 1  | 0  | 5  | 0  | ULT3580-TD5  | 00078A2xxx | F990 | 78221170xxx| |  
 | 7  | 1  | 0  | 6  | 0  | ULT3580-TD6  | 00078B7xxx | F9A0 | 78221170xxx| |  
 | 8  | 1  | 0  | 7  | 0  | ULT3580-TD6  | 00078B7xxx | F9A0 | 78221170xxx| |  
 | 9  | 1  | 0  | 8  | 0  | ULT3580-TD6  | 00078B4xxx | F9A0 | 78221170xxx| |  
 +----+VVVV+VVVV+VVVV+VVVV+VVVVVVVVVVVVVV+VVVVVVVVVVVV+VVVVVV+VVVVVVVVVVVV+-+  
                                                                               
     Please select a device by entering the number in the leftmost column      
     of the list followed by enter.                                            
 [S] Scan                                                                      
                                                                               
                                                                               
 [H] Help   [M] Main Menu  [V] Toggle View                                     
<[Q] Quit | [P] Previous | [N] Next | Line # | Command >

If you have more drives, 'N' for next screen, otherwise, chose the drive by first column number.

     IBM Tape Diagnostic Tool Standard Edition  - Device List                  
                                                                               
       Host Bus  ID   LUN  Model          Serial       Fware  Changer     [#]  
 +----+----+----+----+----+--------------+------------+------+------------+-+  
 | 0  | 1  | 0  | 0  | 0  | ULT3580-TD6  | 00078B3xxx | F9A0 | 78221170xxx| |  
 | 1  | 1  | 0  | 1  | 0  | ULT3580-TD6  | 00078B4xxx | F9A0 | 78221170xxx| |  
 | 2  | 1  | 0  | 2  | 0  | ULT3580-TD6  | 00078B3xxx | F9A0 | 78221170xxx| |  
 | 3  | 1  | 0  | 3  | 0  | ULT3580-TD5  | 00078A2xxx | F990 | 78221170xxx|X|  
 | 4  | 1  | 0  | 3  | 1  | 03584L32     | 78221170xxx| F030 |            | |  
 | 5  | 1  | 0  | 4  | 0  | ULT3580-TD5  | 00078A2xxx | F990 | 78221170xxx| |  
 | 6  | 1  | 0  | 5  | 0  | ULT3580-TD5  | 00078A2xxx | F990 | 78221170xxx| |  
 | 7  | 1  | 0  | 6  | 0  | ULT3580-TD6  | 00078B7xxx | F9A0 | 78221170xxx| |  
 | 8  | 1  | 0  | 7  | 0  | ULT3580-TD6  | 00078B7xxx | F9A0 | 78221170xxx| |  
 | 9  | 1  | 0  | 8  | 0  | ULT3580-TD6  | 00078B4xxx | F9A0 | 78221170xxx| |  
 +----+VVVV+VVVV+VVVV+VVVV+VVVVVVVVVVVVVV+VVVVVVVVVVVV+VVVVVV+VVVVVVVVVVVV+-+  
                                                                               
                                                                               
 [S] Scan           [T] Health Test   [D] Dump         [F] Firmware Update     
 [Y] sYstem Test    [J] eJect Cartrid.[A] CleAning Stat.                       
                                                                               

Chose 'd' to dump the drive

                                                                               
 [H] Help   [M] Main Menu  [V] Toggle View   [O] Other Functions...            
<[Q] Quit | [P] Previous | [N] Next | Line # | Command > d
        Dump ongoing - please wait...                                          
                                                                               
               +------------------------------------------------------------+  
     Progress: |################################################            |  
               +------------------------------------------------------------+

     IBM Tape Diagnostic Tool Standard Edition  - Dump                         
                                                                               
               +--------------------+                  +---------------+       
        Model: | ULT3580-TD5        |       Serial No: | 00078A2xxx    |       
               +--------------------+                  +---------------+       
                                                                               
               +-----+        +-----+                  +---------------+       
        Host:  | 1   |   ID:  | 3   |       Firmware:  | F990          |       
               +-----+        +-----+                  +---------------+       
        Bus:   | 0   |   LUN: | 0   |       Changer:   | 00078221170xxx|       
               +-----+        +-----+                  +---------------+       
                                                                               
               +---------------------------+  Note:                            
        Files: | 00078A2xxx-9068006661.a   |  *.a - before "Force Dump"        
               | 00078A2xxx-9068006661.b   |  *.b - after "Force Dump"         
               +---------------------------+  *.dump.blz - full data package   
               +---------------------------+           +--------------------+  
        Log:   | 00078A2xxx-9068006661.blz | Status:   | PASSED             |  
               +---------------------------+           +--------------------+  
                                                                               
    [R] Return to Device List        

You will see 4 files under your ITDT output directory, you can analysis them if you have tool, or just copy them to your support.