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DLT Data Recovery

Altirium have developed dedicated DLT data recovery methods and mechanisms to facilitate recovery from DLT and SDLT (DLT-V and DLT-S) data cartridges. Dealing with physical problems (stretching, creasing, tearing, heat damage) and the recovery of data following the end of recorded data or read errors.

These are a some of the many symptoms you might experience when there are problems reading or writing data with a DLT cartridge.

DLT Data Recovery Problems Explained

Load "grinding" in DLT 7000/8000 drives

The drive is attempting to read the coarse alignment data that is encoded at the physical beginning of tape, from this data the drive identifies the recorded format of the data on the cartridge. Since DLTIV cartridges can be written in a DLT4000, 7000 or 8000 drive it is essential that the drive can determine which drive made the recording.

The grinding noise in a DLT7000 or DLT8000 drive is from the head positioning mechanism. The read/write heads are mounted in a block which uses a worm-screw for positioning. If a read problem is experienced during the tape loading process then the drive will wind the heads to the furthest extreme, and this is what causes the awful noise.

If the tape was written in a DLT1 or VS80 drive then there is no coarse alignment data and the DLT7000 or 8000 drive will not be able to recognise the tape. The drive might eventually come ready in which case restore the data you need quickly and then retire the tape. If the problem is with the drive then reading in another drive should give you the data without any problems, and the failed drive can be dealt with. Otherwise the only answer will be a data recovery service.

Restore fails with a media or I/O Error

The DLT drive has encountered an area of tape where it cannot read data. Usually the failure will have been preceded by some backwards and forwards tape motion (shoe-shining) as opposed to the usual fairly steady tape motion. The cause of the problem could be physical, and this can usually be determined by noises within the drive, but it often the result of media decay or a poor quality recording.

It might be practicable to kick off a selective restore of files, and you might get lucky and miss the damaged area. The recording is serpentine however so the chances are against you and if there is a physical problem you could well make it worse.

Fluttering or flapping noises

A "fluttering" or "flapping" sound tape loading might well indicate that the leader strip within the drive has become detached. If this is the case then the drive unload light will illuminate and you will be able to eject the tape. The drive will have to be dismantled and the leader replaced or re-fixed.

Such a sound during tape motion, if accompanied by repositioning sounds (shoe-shining - backwards and forwards) indicates that an area of damaged tape is passing repeatedly across the read/write heads. Unfortunately the drive will not stop until it finally gives up and reports a tape read error, and it might snap the tape during the many retries it attempts. The only way to stop it sooner is to switch off the drive, then switch it on and it will rewind - this too could damage the tape. It might be practicable to perform a selective restore of a vital file but this is a risky process. The Serpentine nature of DLT recording means that the damaged area of tape will be re-visited several times and the chances are the problem will be made worse. We advise getting professional assistance for the recovery of data.

DLT cartridge will not unload

If the tape has snapped within the drive then it will not be able to rewind and update its system areas, the tape will not then unload. There should be a whole array of flashing lights on the front of the drive indicating that something catastrophic has happened, and no sound of tape motion.

If you can hear the tape positioning, and periodically there is a "grinding noise" then the tape is intact but the drive is failing to read and update data prior to unloading. The problem could be with the drive or with the tape. You may be able to get the tape to unload by pressing the unload button and holding it in, if not then professional assistance will be needed if the data is required.

Tape remains wound within the drive mechanism

The DLT drive has failed and believes that the tape has mechanically unloaded. Do not pull the tape from the drive unless you really do not want the data back. You will quite quickly render it unrecoverable.

Switch the drive off then insert the cartridge back into the drive enough to prevent further damage, then seek professional assistance. If a tape data recovery is to be successful then the drive will have to be sent with the tape still inserted so that the media can be extracted without further damage.

DLT blank

The DLT has probably been re-initialised (re-labelled), or the backup you want to restore has been overwritten. Specialist data recovery techniques will be required to recover the data.

Last Updated (Tuesday, 30 June 2009 08:45)

 
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