DAT came to the fore in the 1990s across the whole range of computer systems and platforms. The majority of problems during this time have related to tracking, where failing equipment has mis-recorded data on to the tape, and human factors such as the accidental re-initialising of tapes or the overuse of media resulting in tape becoming unreadable due to wear and tear.
DAT is still a popular format, though the latest version has moved from 4mm tape up to 8mm to keep up with the capacity requirements of its market space.
- Drive lights flash, the cleaning light is illuminated and no data can be read
- The restore process fails with a tape I/O error
- A clicking or a buzzing sound is heard from the drive then the restore fails
- The DAT drive lights keeps flashing but the tape will not eject
- The DAT reports no data, or appears to contain the wrong backup set
- The tape is entangled in the drive and becomes severely creased
These are a few of the symptoms you might experience when there are reading problems with a 4mm DAT.
Drive lights flash, the cleaning light is illuminated and no data can be read.
The first action of a DAT drive once the tape has been loaded into the tape path is to locate and read the system area of the tape. This tells the drive how the data is arranged on the media, most notably how the tape is partitioned.
If there is a problem when reading of the system area the drive will work through its retry sequence, this includes unloading the cartridge and re-seating it to see if that fixes the problem.
The cause of the problem could be the drive, it could have failed or require cleaning. If no other tapes have been presenting this problem then there is probably a problem with the tape. If the tape does come ready during a subsequent attempt, presume that it might never happen again and restore your critical data ASAP, then back it up on to a good tape by using a known good drive.
If the tape will not come ready, even in a drive that you know is working properly, then a tape data recovery service is probably the only answer.
The restore process fails with a tape I/O error.
The DAT drive has run into an area of tape where data cannot be read. Usually the failure will have been preceded by some noises from the drive and perhaps even an unload/load sequence. The cause of the problem could be physical, and this can usually be determined by the pitch of the sounds from within the drive. A crease, for example, results in a much smaller are of contact between the head assembly and the tape which causes a higher pitch noise from the drive.
A clicking or a buzzing sound is heard from the drive then the restore fails.
The drive contains a head cleaning brush. If the drive has read problems when attempting to read data from a tape it actuates an arm in the end of which is cleaning material, this is to ensure that the read problem is not the result of "head clog" (a build up of tape oxide that blocks the read/write heads). The fact that the restore then fails indicates that this was not the problem and there is probably something wrong with the tape or the recording.
It is possible that a selective restore attempt might enable you to restore some of your most critical data but be cautious as any physical damage might be made a lot worse. If the tape snaps and wraps around the head assembly then large volumes of data could be lost.
The DAT drive lights keeps flashing but the tape will not eject.
If there is no attempt by the drive to unload and re-seat the tape, and no noisy self clean sequence then it is probably that the tape has either snapped or become detached from one of its reels. If the tape snaps then it is likely to become wrapped around the read head assembly and specialist help will be required to remove the tape without causing further damage so that the data can be recovered.
If the tape becomes detached from either reel then there has been a serious internal failure within the drive as this takes considerable force. A light source and sensor pair detect the physical end or beginning of tape when the transparent leader tape passes and lets light through. If either fails then damage can occur, though it is unlikely that the tape will become entangled within the drive.
DAT records from the start to the end of tape and does not use a serpentine format. This improves the chances of a successful tape data recovery as, once data can be accessed from beyond any damage, it is likely that the remainder of the tape can be read.
The DAT reports no data, or appears to contain the wrong backup set.
If it is the correct tape then this usually indicates that the tape has been erased or re-used. The prospects for data recovery depend upon the extent to which the required data has been overwritten.
There is no method for positioning the media beyond the most recent data without resort to tape data recovery procedures, and even if you could get into the original data your backup software would never understand what it found. A competent tape data recovery company will be able to recover all existing data and from this rebuild your files.
The tape is entangled in the drive and becomes severely creased
The drive has damaged the tape during either loading or unloading, most likely during unloading. You will have seen the drive going through its re-seating process to reload the tape and heard some quite alarming noises as the drive attempts self cleaning. To get the data back will require a data recovery service.
The recording technique used with DAT does improve the chances of a successful data recovery in many instances where there is physical damage. DAT records data from the start to the end of the tape, as opposed to serpentine formats where multiple passes along the length of the tape are made. This means that one the tape is positioned beyond the point at which a failure was encountered there is no reason for the drive to return to that point along the tape.
