• Error Rates (Recoverable)
  • Read error rate = 1 in 1x10⁷ detected
  • Read uncorrected = 1 in 1x10¹⁷ bits
  • Read undetected = 1 in 1x10²⁷ bits
  • Write recoverable = 1 in 1x10⁶

DLT bad media example

SDLT

From the outside, the Super DLTtape cartridge looks very similar to the DLTtape IV cartridges. The basic geometry, write protection switch, and label space are unchanged from the DLTtape IV cartridge. This simplifies the integration of Super DLTtape into existing operating environments and into automated tape libraries. The Super DLTtape cartridge is easy to recognize; it has a different color than the DLTtape IV cartridge and contains a distinctive pattern molded into the shell. The Super DLTtape cartridge has a keying feature to insure it can’t be loaded into previous generation DLTtape systems.

Write

During write operations, the DLTtape drive assures that the data written is correct by performing a read after write. If an error is detected, the drive rewrites the data block (see Figure 6-3) further down the tape until the read-after-write check validates that the block is now correct. In addition, the drive records powerful Reed-Solomon ECC blocks on tape.

Read

During read operations, if an error occurs, DLTtape drives recover the data using powerful ECC code. DLTtape drives can recover up to four bad blocks of data within a 20-block entity. At a recording density of 62.5Kbits per inch, four consecutive blocks translates to two inches of DLTtape media. That means that, even if as much as two consecutive inches of tape are damaged on a single track, a DLTtape drive can recover the data.

Getting a lot of 'Unreadable media' on fairly new tapes. No other indication of need to run tape cleaner. Should I run tape cleaner?

Media can have many defects, the design of the drive is such that it will easily work through these without any problems. It is impossible to manufacture perfect media. If you encounter media with too many errors out of the box make sure it is a supported brand, Maxell, Fuji, Quantum, Compaq and several others are approved for DLT use. Make sure the media has been stabilized at room temperature for 24 hours before using. Inspect the media using the procedure described in the Media Care and Handling document available on our web site. Instead of running a cleaning tape through the drive try placing another know good tape into the drive. If this tape works then you might want to try running a quick erase or full erase(may take up to 4 hours)on the tape giving you troubles. If this does not work and the rest of the tape works fine you might want to take the tape back to the manufacturer or reseller to get another one.

From the Quantum Knowledge Base