Dell PowerVault 136T LTO Handbook page 18

This can happen for 3 reasons.
•
A head clog
•
A hardware failure on the drive
•
Bad or marginal media. (see Troubleshooting Cleaning/Read/Write errors)
Note-1: Run Dell Online PowerEdge
Note-2: Dell Online Power Edge Diagnostics does not support Dell PowerVault 110T LTO (see figure 1)
Dell LTO Media Handbook
TM
Diagnostics to determine media or hardware related failures.
Page 18