The DLT technology is based on a high-capacity, streaming-cartridge tape that uses a dual-channel read/write head and DEC's proprietary data-compression and compaction schemes. We
tested three drives
in this category: the Quantum DLT2000, the TTI CTS-2110, and the Overland Data DLT 2000. Before Quantum acquired the DLT technology from DEC last October, DEC was the only manufacturer of DLT drives. These DLT drives offer an uncompressed capacity of 10 GB, compared to 4 GB for DAT drives and 5 GB for 8-mm helical-scan drives.
DLT drives offer several advanced features, such as full SCSI-2 command-set implementation, sophisticated LED indicators and built-in diagnostics, high data compaction with 2 MB of read/write data cache memory, and a high data transfer rate of 1.25 MBps in native (i.e., uncompressed) mode. These features make the
m suited to high-capacity network backup and archiving applications.
In contrast to helical-scan technologies, which place data in slanted stripes, DLT drives use a linear, serpentine recording method that places data in longitudinal tracks. The drives can read and record multiple channels of data simultaneously. This longitudinal recording method allows you to add parallel channels of read/write elements to the head to increase performance.
Assuming a 2-to-1 compression ratio, DLT drives can achieve data transfer rates of 3 MBps. The heads are stationary, which increases the life spans of both the heads and the tapes. The life spans exceed those of helical-scan technology tape drives. During read/write cycles, the tape runs past the drum at 100 to 125 inches per second. Fast-search rates are even higher. Quantum guarantees that its tapes will maintain their integrity for at least 500,000 passes, and the life of the heads is estimated at 10,000 hours. In comparison, 8-mm helical-scan tapes last
only 2000 hours.
Twenty-five percent of the data on DLT drives is dedicated to error detection and correction. A custom chip based on the Reed-Solomon algorithm--and software--maintains strict data integrity. For every 64 KB of data, there is 16 KB of ECC (error-correction code). Sixty-four bits of CRC (cyclic redundancy check) error-detection code tag along with every 4 KB of data, and there's also an overlapping 16-bit CRC on each record.
The DLT drives we tested consistently outperformed all the other types of tape drives. Among the three DLT2000-based drives, the Overland Data DLT 2000 edged out the others, in both the Windows NT backup tests and the workstation-attached runs, with ARCsolo 3.02 backup software. The Overland Data DLT 2000 is the most expensive of the three drives we tested, but it posted solid scores in usability and features. All three drives are manufactured by Quantum and present excellent value. The Quantum DLT2000 has the lowest price, and its scores were solid--basicall
y, it's the best buy for the money.
DLT Drive Winner
We selected the Quantum DLT2000 for its solid performance and good scores in features and usability. Its suggested retail price is also the least expensive among the DLT drives we tested.
TABLE OF DLT FEATURES
Overall
Price Workstation NT
Quantum DLT2000 $4650 9.50 9.46
Overland Data DLT 2000 $6000 9.57 9.58
TTI CTS-2110 $4995 9.50 9.39
Performance
Workstation NT
Quantum DLT2000 9.99 9.94
Overland Data DLT 2000 9.98 10.00
TTI CTS-2110 10.00 9.85
Features Usability
Quantum DLT2000 *** ***
Overland Data DLT 2000 ***
***
TTI CTS-2110 *** ***
(All DLT drives use Quantum's DLT2000 drive mechanism.)
Key:
Excellent ****
Good ***
Fair **
Poor *
photo_link (32 Kbytes)
The outside cases of the three DLT drives we tested are virtually identical. All are manufactured by Quantum. Clockwise from the top: TTI's CTS-2110 drive showing its LED panel on the front (which the other drives don't offer), the back of Overland Data's DLT 2000 drive showing its SCSI ports and fan, and Quantum's DLT2000 drive.
DLT Drives
