Data Recovery of Storage Tapes

Tape backup used to be the standard for computer system backup. In the early days tape costs were significantly lower than those of a disk based solution. Hard drives came at a premium price and were prone to failure.

Technology has improved and the price of hard drives has taken a steep dive compared to a couple of decades ago. Tape drives are still used as an inexpensive means of backup today on many medium sized and enterprise systems. You'll find many mainframes still using tape for daily backups.

During the bygone era tapes were manually loaded by an operator when a request was made. The tape had to be selected, loaded then the data located and made available to the user. It took several minutes before the data was available.

The larger tape systems today are all handled mechanically with a robotic system locating the tape and retrieving the appropriate information. Data retrieval time has been shortened but the system would be horribly slow for quickly locating gigabytes of information as compared to the modern hard drive.

How Data is Stored on Tape

When storing data on tapes it uses the same concept as the hard drive. Information that consists of magnetic ones and zeroes is written to the media. This is where the similarities end. Due to the way tape is transported data is written from beginning to end. This is called a sequential read write process. If the information is near the end of the tape it must be read from the beginning to that location.

A hard drive can be written to at the beginning, end or any position in between as determined by the write head location. This type operation is called random access. The head of the drive travels directly to the data location.

The above techniques affect how data may be recovered from a tape. Each time a tape records data it leaves a blank marker space at the end which signifies the end of the data on the tape. If the tape had 400MB of data on it and it is used to back up 100MB of data then the data after the 100 MB end marker and the data that the 100MBs of new information has overwritten can't be read or retrieved by normal means. It will require a data recovery service.

Data Recovery

Data is recorded to tape using three fundamental systems. The multitrack parallel system records 9 parallel tracks of data from beginning to end. The Helical Scan system records data much like the VHS video recorder the tape wraps around a cylinder that has read and write heads that impart the data to the tape as it moves by. The Serpentine method writes parallel channels of data in one direction from end to end then does the same in the other direction. It can literally be a hundred tracks. These data recording methods can present special challenges for data recovery.

Data recovery services should be contacted in any of the following conditions.

Physical Damage

There could be damage to the tape itself. This would include badly twisted, creased or broken tapes. The condition could also include tapes that are old and deteriorated and have lost magnetic properties on the coating.

In other instances the tape may not be damaged at all but there is a failure in the mechanism that contains the tape. Cartridge shell damage may occur in the form of broken wheels or rollers. Other forms of damage may include fire or water damage.

The good news is that in these situations most recovery services are able to recover approximately 98 percent of the data on average.

Logical Damage

Logical corruption occurs when there is a failure in writing information to the tape. This could result from a failed controller or misaligned write heads. In either case the data is no longer readable. In these cases the recovery service will use special software that scans the data several times attempting to piece it back together. The software has the ability to substitute dummy blocks where data is irretrievable to recreate the file.

Success rates vary in this scenario due to the complicated writing schemes employed in these systems but much of the data can be recovered.

Tape Data Recovery Services

When contacting a data recovery service for tapes a quality provider should take the following steps.

The tape should be examined in laboratory conditions and the damage assessed.

A copy of the tape should be made. The copy should be examined to determine the best procedure for data recovery.

You should be contacted at this point with an estimate of costs.

Your approval should be given before any recovery process begins.

As with hard drives and other media data recovery from tapes are part of the norm and usually a high percentage of your data can be recovered.