Symmetric Phase Recording In DLT Tape Drive

The SDLT data tape format has unique attribute of “buckling link” that helps in providing strong engagement with S-DLT backup tape drives. The enhanced modular design of the SDLT tape drive is drawn together on robotic production line. So the manufacturing flaws are checked automatically and the human interference is also minimized. Magnetic data tapes in comparison to the hard disk drives are much cheaper and are better data storage medium for long term. Data tapes are best for data replication at remote sites and their cost is also low. The users of magnetic data tapes can easily keep the data at remote locations and its maintenance is inexpensive. Data tape is ideal storage medium for recovery in case of disaster. Now with the fiber optic networks, the archive data can be taken to the site by the users and there is no need for physical movement of the data tape off the site.

In 1980’s a new technology was developed by DEC (digital equipment Corporation) and ½ inch standard magnetic data tape was the base of the technology. First true system of digital linear tape (DLT) was developed in the year 1989. Afterwards Quantum acquired this DLT tape technology. This tape technology has been licensed subsequently by different Original equipment manufacturers (OEM) for the production of automated backup data tape libraries. DLT tape technology is an effective adaptation of magnetic data recording mechanism (reel to reel) in which the data tape drive performs as 1 reel and the cartridge as other.

Width of the metal particles used in the digital linear tape drives is half inches. The width of the particles of DLT is 60 percent more than that of the 8-mm data tape. DLT tape drives write the data onto the tape reel in pattern of “serpentine”. The tracks on the DLT tape reel are organized into pairs. Each of the data track on the tape reel goes along the entire DLT tape length. When the data is written onto the tape reel, the first track set is written on the entire tape length. The tape heads of DLT tape drive reposition themselves for recording new track set after reaching to the tape end. Afterwards the DLT data tape is again recorded along the whole tape length but the direction of recording is opposite this time. This back & forth data recording mechanism continues until the entire DLT tape reel is full. The current DLT backup tape drives either record 128 tracks or 208 data tracks.

New mechanism of SPR (symmetric phase recording) is used in DLT drives for achieving higher data density. In this symmetric phase recording process, the pattern of data is angled on the adjacent data tracks. SPR increases the track density and the guard bands are also not needed because the pattern of SPR is “herringbone”. The HGA (head guide assembly) of the DLT tape drive has unique design. HGA of the DLT tape drive is made of aluminium and its shape is like a boomerang. HGA has 6 big mounted bearing rollers. In the helical scan mechanism the tape is grabbed from the middle and it pilled into place. But in guide system of DLT tape drive a leader strip is linked on the tape reel end and is pulled out of the DLT tape cartridge. Then it is guided around the HGA in smooth arc and is tenderly wrapped around take up data tape reel in the DLT tape drive.  The tape is not pulled by the rollers but instead they guide the tape reel.

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