High reliability comes from data redundancy. The LTO Ultrium format uses Error Correcting Code (ECC), generated at two levels (C1 and C2), which is added to the data. The data is then recorded on the tapes. This logical format provides quadruple redundancy of data, making it possible to recover data when reading problems occur.
With the Ultrium 4 tape drive, data is written using 16 heads and each tape is divided into 4 bands. For each band, each head goes forward and backwards on the tape 7 times, writing 14 tracks. This means that with 16 heads, 224 tracks are written per data band. And as there are 4 data bands, 896 tracks can be written in total.