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Volume.6
FUJIFILM & JEITA News Letter
Can you trust LTO?
The quantity of digital data has been sharply increasing rather than before thanks to developing big data and Internet of Things (IoT). Recently more people have chosen magnetic tapes in order to archive digital data for a long time. A magnetic tape has huge storage capacity and a strong point that it can take off from a tape drive and store outside a drive. It is suitable for a long term storing. In addition of these advantages such as “Large Capacity” and “Portability”, let you know another specialty of a magnetic tape. It is “High Reliability”. This letter will mention one example of “High Reliability” with a magnetic tape.
1.Data Writing
The most important thing of writing data is to write readable data on recording media accurately. To realize this, the LTO tape drive implements two technologies, "Read While Write" and "Rewrite".
(1) Read While Write
"Read While Write" is a function to check whether the written data can be read from the tape immediately after writing data to the tape. When it confirms that the written data can be surely read, writing operation is completely finished.
(2) Rewrite
Can you guess what happens if the function of “Read While Write” finds that written data is not completed and writing operation cannot be finished? Then “Rewrite” will act. The function is to rewrite as the word but it does not only rewrite but also use the different reading head and rewrite to the different place. For instance, “Rewrite” can write data to the different place accurately even though one part of tapes are not writable due to physical scratches. “Read While Write” and “Rewrite” realize that LTO tape drive write correct data to the tape.
2. Data Reading
Even though a tape can write data, it has possibility of becoming difficult to read recorded magnetic signals because of external factors such as high temperature/ high humidity/ dust. However under the situation, LTO tape drives can read accurately. This function is “Error Correction Code (ECC)”. “ECC” writes a value called parity calculated from the data. If data is broken and cannot be read, “ECC” can revive data from parity. “ECC” is included in not only LTO but also data storages. But “ECC” of LTO is the strongest to revive data. When 15% of all data inside LTO cannot be read, there is no problem to read them again perfectly.
In these ways, the tape drive has the function to reliably write data to tape media and the function to correctly read the data even if there is some damage in the written data. Thus, it realizes that tapes can provide “High Reliability”.
※Information from JEITA mail magazine.
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