DLT

Descended from the DEC TK range of drives, the DLT has emerged as one of the major players at the high data capacity and high performance end of the market.

Serpentine recording format

DLT utilises a recording style known as serpentine. Recording takes place as a sequence of track pairs running alternately from beginning of tape to end of tape and then back again:

This method of recording allows high speed operation and search. To locate a particular section of data on tape the drive can step across tracks until it is close and then search along the tape.

At Kroll Ontrack we have extensive experience with the recovery of data from DLT tapes from all round the world, often referred to us from other data recovery companies.

Overwrite

DLT is a very reliable tape. The majority of the problems that we see are the result of human error. Accidentally re-initialising a tape, or forgetting to enable the append option before starting a backup are common problems.

Media failure

An error caused by a recording flaw might affect more than one data track and so an error might occur each time the drive passes that point on the tape. If the problem is the result of physical damage then you could be putting your data at further risk by attempting to read as the tape could break.

Reference Track damage

If the reference track at the beginning of the tape is damaged then the drive will not be able to identify the recording and you will not be able to restore from your backup.

DAT

Derived from the SONY Audio DAT recorder and a joint HP/SONY recording format, DDS, DAT has rapidly become the most popular medium for tape backup.

Companies such as Hewlett-Packard have put great effort into the development of the 4mm DAT drive and are continuing to do so.

Format is high capacity with good performance combined with drives and tapes which are of relatively low-cost.

The recording method used is helical scan. Data tracks are recorded diagonally across the width of the tape:

We have developed hardware to cope with a vast array of problems from human error to hardware failure.

Overwrite

The data that has been overwritten is lost, but all older data from further along the tape will be recovered.

Media failure

We can move past any damage and recover the data that we find. The recording is made in one direction only and so the damage is never re-visited.

Mis-track

Kroll Ontrack has developed sophisticated equipment to allow the rapid adjustment for tracking problems with tapes.

System area damage

If the system areas at the beginning of a tape are damaged then the tape will appear to be blank. Your data will still be there and Kroll Ontrack will recover it.

Exabyte

Derived from the Sony Camcorder mechanism, but with improved data integrity, Exabyte's 8mm backup device became prominent in the 1980s as a high capacity backup device for DEC VAX systems.

Exabyte have continued to enhance the mechanism and improve the recording technique as the drive became popular for high-end networks and UNIX systems. The latest drive, the Mammoth, is capable of recording up to 40 gigabytes of data at extremely high speed.

The recording method used is helical scan. Data tracks are recorded diagonally across the width of the tape:

We have developed hardware to cope with a vast array of problems from human error to hardware failure.

Overwrite

The data that has been over-written is lost, but all older data from further along the tape will be recovered.

Media failure

We can move past any damage and recover the data that we find. The recording is made in one direction only and so the damage is never re-visited.

Mis-track

Kroll Ontrack has developed sophisticated equipment to allow the rapid adjustment for tracking problems with tapes.

System area damage

If the system areas at the beginning of a tape are damaged then the tape will appear to be blank. Your data will still be there and Kroll Ontrack will recover it.

Quarter inch cartridge

Quarter inch cartridge is a well-established recording medium which predominated in the UNIX/PC environment prior to the advent of 4mm DAT. It also found favour with IBM as a main backup option for the first AS/400 mid-range systems.

The only current manufacturer of these drives is Tandberg Data. There are still many drives in use from other manufacturers such as Archive, Wangtek and Sankyo.

The recording method used is serpentine. Data tracks are recorded alternately forwards and then in reverse:

Overwrite

We can recover all data that has not actually been overwritten. The complication with QIC is that a full-width erase bar is energised during the recording of the first track. This is to ensure that the drive is writing to blank tape and thus avoid any problems with earlier data. It does mean that once a whole track has been written, the remainder of the tape has been erased.

Media flaw

Kroll Ontrack can recover all of the data beyond a media flaw, even though your backup software refuses to read any further.

If the problem is restricted to the current track then the remainder of the data will be recovered intact.

Tracking

Kroll Ontrack can recover data even after a serious drive failure. At Kroll Ontrack we have even recovered data written by a drive where the recording heads had almost fallen off.

DC2000/Travan TR1, TR2 and TR3

The lowest cost tape systems are those designed to be connected to a computer's diskette controller. These are known as DC2000 or mini data cartridge drives.

The most modern of these use Travan and QIC Extra cartridges and many have multi-gigabyte capacity.

Accidental erase or blank tape reported

This might simply be damage to the Volume Table at the start of the tape. Kroll Ontrack has developed software to identify files from the data without the need to reference the tape Volume or Directory information.

Damaged file

Some applications report file damage when they fail to locate a file within a data set. Often the data is not actually damaged and so Kroll Ontrack utilities can recover your data.

Snapped tape

Kroll Ontrack has years of experience with damaged cartridges and can recover the data from all undamaged areas.

Optical and WORM

Kroll Ontrack has developed hardware and software to cope with a wide range of problems with optical disks.

System area damage

When damage affects the defect tables or other system areas of an optical disk the media becomes totally inaccessible. Ontrack Data Recovery services can perform a low level read of the intact sectors.

Kroll Ontrack has developed software to rebuild the defect lists to allow for logical sector reads from the recovered disk image. Even when the damage has been extensive Kroll Ontrack has been able to recover large numbers of files intact.

Media flaws

Ontrack Data Recovery services have a vast array of disk recovery software allowing for the recovery of files even when file system management areas of the disk have been rendered unreadable.

Files can be recovered just as they can from damaged hard disks.

Physical damage

Scratches and gouges will affect the performance of the optical disk laser and reduce read effectiveness. Kroll Ontrack has developed techniques to reduce the effect of physical damage and so read all but the most severely damaged sectors.

WORM formats

Kroll Ontrack programmers have processed data from a wide range of Write-Once Optical systems and have the depth of experience to deal with new formats whenever they are encountered.