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The long and winding DLT
Posted by Mark on Oct 18, 2008
Tape is tough, but really …
As a data recovery engineer pretty well nothing comes as a surprise. We have received DLT cartridges where the tape has snapped, been overwritten, even where it has been submerged in flood water for over a week.
Nothing, though, has been quite as bizarre as the empty DLT case that arrived, along with a supermarket carrier bag crammed full of unwound tape. What was going on?
The IT person, it transpired, had ejected the DLT data cartridge only to find that the case came out from the drive but that the tape was still wound into the drive. Thinking that it was just the end of the tape that was stuck he began to pull the tape from the drive. After a few feet he started to think this was odd, but that it must be close to the end by now.
A couple of hours later the end of the tape finally appears, but the floor was covered with tape, and tape that was tangled, had been trodden on and was generally in a poor state.
For information, if you ever find yourself in this situation just STOP winding, better still do not start. There are was to get the tape sorted out and back on to the reel, but once it is unwound and damaged then data recovery is the only option if you want the data back, and even that is a long shot.
Manually winding a DLT from one reel to another takes about 4 hours. When it has also to be untangled then you can multiply this a few times. This one took about 3 days, but having seen every inch of the tape we knew the prognosis was poor.
Some data was recovered, but no-where near the volume ideally required. The damage was less towards the end of the tape so some data could be recovered intact, but the first 80% was in a terrible state and all of the data was lost or damaged.
The moral of the story? Stop and think. Initially the only problem had been that a tape sensor problem had allowed the tape to wind fully onto the reel within the drive and so it was no longer connected to the supply reel within the tape case. This could have been easily rectified, but the action taken turned an irritation into a catastrophe.
