Tracking System In DLT Tape Technology

The guide and tape contact is minimized in the DLT tape drive as the guide rollers have gentle wrap-angles around them. The tape reel’s recorded side does not touch the guide rollers so it helps in minimizing the tape wear. The tape’s reading and writing speed, deceleration and acceleration is controlled precisely by the automated dual motor mechanism in the DLT tape drive. The drive also has self cleaning system. DLT tape drive has 2 islands that are non-energized. They help in continuous cleaning of the DLT tape reel and ensure data integrity and precise contact of tape & drive head. Therefore the head life of the DLT tape drive prolongs to about 30,000 hours while that of the helical scan 8mm devices is about 2,000 hours.

Multiple channels are used concurrently for reading and recording of data in DLT tape drives. Data tape media in the DLT tape format is divided into horizontal parallel data tracks. The tape reel then runs past an immobile tape head and the Data is recorded onto the tape. Two channels can be recorded at the same time by the use of 2 write/read head elements that efficiently double the transfer speed at given possible recording density and tape drive speed.

The process of reading and backup of the large data blocks is speed because of the high transfer speed of DLT tape drive. MR (magneto-resistive) tape heads and the thin film further increase the recording capacity, bit density and the transfer rates. As the quantity of simultaneous channel recording increases, the transfer rate of data also increases. Overall throughput of the tape drive mainly relies on the tape drive’s capability of tracking the data transfer speed of host system. If the host system’s data speed is slower that that of the tape drive, then the performance degrades as the tape stops and has to frequently reposition.

The performance and output of DLT tape format is optimized as an efficient adaptive feature of buffering cache has been incorporated in the DLT tape drives so that maximum throughput could be achieved. The delays because of the repositioning are minimized and the throughput of tape drive is improved due to the feature of buffering cache. The buffering cache monitors the system of host and the operations of cache buffering are adjusted dynamically so that it can match with the host system’s transfer rate.  

The time needed for file location can be another criterion to check the performance of the tape drive. This measure is very much important in the applications (near line) like the manipulation of image which searches files frequently and restores or appends data. Search time is minimized in the Digital linear tape technology as at the data tape’s logical end, there is there is located a file-mark index. The index holds the address of tape segments of each tape files.

The drive moves to the track that has the specific required file and then fast speed searching is performed to the file. With the help of this powerful feature, the DLT tape products are capable of finding file with average 45 seconds time in data tape cartridge of 20GB. Multi-layer mechanism helps in achieving this remarkable data integrity in DLT tape technology. Reed Solomon 16KB ECC with user data of 64 KB, error detection code (16 bit) for each data of 4 KB, cyclic redundancy code (64 bit) and overlapped cyclic redundancy code on each record of user is interleaved by the ASIC (application specific integrated circuit) chip. 

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