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REVIEWSWhat's Up With DAT? Backing Up Your Network Data On 4mm Drivesby Jeff NewmanAlthough digital tape storage is a slower medium than high-speed primary server storage devices, such as today's hard drives, tape media is an invaluable asset for disaster recovery. When coupled with a good backup software package, it can help you with "I didn't mean to delete it!" panic removal and it's one of the most inexpensive solutions for off-loading less frequented files, preserving more expensive high-speed magnetic storage. In our San Mateo lab, we tested seven state-of-the-art 4mm external digital audio tape (DAT) drives that offer more than twice the capacity, more than twice the spee d and a media size twice as small as those offered in the past. Of all the drives that we tested, Hewlett-Packard, Sony and Conner were the only vendors that actually manufacture their own drives. All of the units offered 4 GB to 8 GB capacity, support for digital data storage (DDS), DDS-2 and DDS-DC tape formats, 1-MB on-board cache and a SCSI-2 interface. To divide the field, we examined price, performance, features and drive warranty--a tough challenge given the fact that four of the seven products tested are repackaged drives. Top honors go to Conner, due its price, performance and three-year warranty. Hewlett-Packard also did well, because of its overall performance. All of the drives we tested were excellent, and the performance differences were almost negligible. Each of the original manufacturer's drives had better performance in at least one of our tests. Conner CTD8000E-S  Conner's CTD8000E-S was a solid unit, earning exceptional marks throughout our testing. As with all the drives in this roundup, performance was excellent given our hardware/software configuration. Compared with Hewlett-Packard and Sony, its performance was even at best, but it had the best streaming transfer times. Conner also offers the best warranty--three years, as opposed to the two years HP and Sony offer. Hewlett-Packard SureStore Tape 6000 The HP SureStore Tape 6000 finished a close second and offered slightly better restore rates with both directory-intensive and streamed data restorations. Hewlett-Packard uses the helical scan method for reading and writing data to the tape, which is defined in the DDS-2 standard. Although a str ong contender, HP's unit placed second because of its one-year warranty. If a longer warranty isn't too high on your criteria list, HP is worth a look. Sony SDT-7000Sony manufactures the tape carrier for its SDT-7000, but it lost out to others, due to a lack of features and limited warranty. It was also the most expensive of the three original manufacturers. We tested Sony's internal drive, priced almost $500 more than Conner's external drive, and even more if you add the cost of an external SCSI conversion kit. It might be worth the price if Sony offered slightly better file/directory intensive backup times than HP and Conner. The SDT-7000 was very close to Conner for file/directory-intensive restores and relatively even with HP for streamed backups and restores. Repackaged OEMsAlthough neither HP, Sony nor Conner offers any fancy drive features, some repackaged drives from other vendors do. Features like LCD reado uts of drive status, transfer rates and remaini ng tape capacity reporting are good, but they typically come at an extra price. While their worth is questionable considering the level of media management that today's tape backup software packages offer, hardware-based added value can be a differentiator when looking at tape drives. TTI offers a Sony SDT-5000 DAT drive, packaged with an LCD display that shows drive status and a data quality report with a display of the percentage of rewrites during backup and tape capacity remaining. It is also equipped with an external toggle button that allows data compression to be turned on or off. The Sony SDT-5000 drive is an older version compared with Sony's SDT-7000 and performance was slightly, but consistently, lower than other tape drives we tested. All other features and warranty are identical to the newer SDT-7000. TTI also offers a two-year warranty. Emerald Systems uses HP's carrier for its GemStor. Although slightly less expensive, the GemStor adds nothing--there are no value-added fea tures and no warranty. Emerald positions this unit as a low-cost, no-frills solution. The ADIC DATa 8008D and ANDATACO Encore Plus 4001S also offer HP drives but add display panels that show status information, such as total data transferred, remaining tape capacity and drive status. Both offer similar performance and a better warranty--doubling HP's one year--but they are significantly more expensive: amounting to over $1,000 more in the case of ADIC and more than $1,500 in the case of ANDATACO. Jeff Newman can be reached at jnewman@nwc.com. DDS-3: Stuffing In The DataEven though tape manufacturers have managed to double the performance and capacity of their existing tape drives, they are not stopping there. DDS-3 is in the works, which defines the specification to double the capacity of DDS-2 drives on existing 4mm x 60m, 90m and 120m tapes. These new drives are expected to store 12 GB of data onto a 4mm x 120m tape natively. With compression, the se new drives will be able to pack 24 GB of data onto the same length tape without performance degradation. How We Tested Backup And Restores With DAT DrivesWe tested seven DDS-2 DAT drives in our San Mateo lab on a Dell P60 EXP machine using an ADAPTEC 2940 PCI SCSI host adapter. All tests were performed with 120m tape with compression turned on for each drive. We used Arcada's Backup Basics for backup and restore testing. This allowed us to eliminate data management overhead and automatic software compression that many comprehensive backup solutions offer. The tests consisted of both file- and directory-intensive backups (14,337 files/668 directories--728,050,020 total bytes of data) as well as streamed data (A 1-GB highly compressible file/zero directories). Restores were performed with the same data, in the same manner as defined above. Note that the rates indicated for each drive are relative to the equipment and software used for testing and will differ on varying equipment using comprehensive and optimizing backup solutions. As an interesting comparison, we include performance numbers for an Exabyte 8500 8 mm tape drive as well as a high-speed Quantum Fireball 1080S hard drive subjected to the same tests. March 11, 1996 |
