In general tape data cartridges have a high level of reliability, but when problems do occur it is often when attempting to restore your data. Fortunately, the tape media becoming unspooled leads to the data cartridge being unusable and for cartridges using a single spool, the tape drive will need to be repaired.
If the tape media unspools into the tape drive and the data stored on it is important, the tape drive should be sent for data recovery, before it sent to be check for any damage which may have occurred. It is also best to send the data cartridge, even if you believe it is empty, as it may allow us to determine the cause of the problem.
Unspooled Tape Media
Fortunately, it is rare for the media used in cartridges such as DLT, Super DLT and LTO data cartridges to unspool into the drive. No attempt should be made to remove the tape media from the drive, as it must be removed carefully to avoid any damage occurring. This is a job best left to a professional data recovery specialist.
There are two reasons for tape media to become unspooled from a cartridge which uses a single spool, either a fault in the tape drive “end of tape” detection circuit or a problem with the media itself. The most common method for determining the end of the media is using sets of holes, which are detected during the movement of the tape, but a failure to detect them will result in the media spooling off the cartridge.
One set of media which uses two spools, such as Quarter Inch and Mini-QIC data cartridges detects the end of the media using the same method of holes in the media, with light shining through a prism fitted in the cartridge. For cartridges such as DAT and AIT cartridges the media is fixed each spool and relies on the detecting information in the tracking area. When rewinding the tape, it will often wind tight using media fixed to the empty spool to stop the tape. A failure of either will result in all the media being spooled on only one of the spools.
Unspooled Tape Data Recovery
The data written to a tape which has unspooled should be unharmed, although if it occurs when writing a backup, the dataset will be incomplete, but all files backup up to that point should be safe. If the media itself has been overused, there may be damage to the data stored on the media, which is why media rotation is extremely important.
Never attempt to fix the problem yourself, as it may result in further damage. In many tape data cartridges, the end of the media is not affixed to the spool, which is an important safety feature. Using sticky tape to the fix the media to the spool could result in the further damage occurring to the media, particularly if the end of tape detection mechanism has failed, either in the data cartridge or the tape drive. Such actions could result in the media becoming tangled. Always send any unspooled data cartridge for professional tape data recovery.