Some tape drives that support linear tape formats, like IBM's TS1120 and Sun's StorageTek T10000, are taking steps to minimize the occurrence of backhitches. These two drives have a speed-matching feature that automatically changes the speed of the tape by sensing the incoming speed of the data. The TS1120 includes six options--50MB/sec, 60MB/sec, 70MB/sec, 80MB/sec, 90MB/sec and 100MB/sec--while the T10000 provides two speeds, 50MB/sec and 120MB/sec.
In shops deploying a disk-to-disk-to-tape backup process, the time restrictions to move data to tape are generally less constraining than when backing up data to disk. For users with longer windows to move the data from disk to tape--and who are less concerned about fast restore and access times--larger, slower moving tape formats like DLTtape S4 or SAIT may be the best choice. For instances where it's necessary to quickly move and restore data to and from tape, formats with higher native throughputs, like LTO or the StorageTek T10000, should be considered. Users employing tools like hierarchical storage management and accessing data on tape, may prefer 3592 tape formats that include "mile posts," markers on the tape at four-meter intervals that help pinpoint where the data lies. If data encryption is required, higher capacity tapes may be preferable because encryption eliminates the option of compressing the data.
Tape's actual cost
The final reason to use--or not to use--a higher capacity tape is financial. DLTtape S4 delivers roughly double the native capacity of SAIT-1 and LTO-3 for approximately the same price. However, buying tape based strictly on the cost per gigabyte doesn't take into account other cost-related issues, such as the need to upgrade tape libraries. Managing data on larger capacity tapes may also be a concern. "Capacity is getting so large that users can't use all of the space on the tape," says Richard Leonarz, marketing manager for tape storage in Sony's Media & Applications Solutions Division.
Each succeeding generation in the "super tape" category becomes quicker and holds more data in a Sisyphean effort to keep up with growing data stores (see "What's a 'super tape'?").
But jamming more bits onto a tape introduces new compatibility and usage problems. LTO-3 tape drives can read and write LTO-2 and LTO-3 tape cartridges, but read only LTO-1 tape cartridges. SAIT-1 and StorageTek T10000 tape drives can only read and write to their respective SAIT-1 and T10000 tape cartridges; they can't read or write from older AIT, 9840 and 9940 tape formats. And as tape capacities and data transfer rates increase, users need to ensure that the tape drives supporting these formats can adjust tape transfer rates to match the slower speeds and feeds their infrastructure will likely produce.
WORM tape
Though relatively small, the demand for WORM tape is growing. Suppliers of LTO and SAIT say their WORM tape sales are between 2% and 5%, while Sony reports that sales of its SAIT WORM tape accounted for 7% to 9% of its total tape sales in the last six months.
Tape vendors implement WORM technology in very different ways. DLTtape S4 and SDLT 600 tape formats don't require a special tape cartridge to store data in a WORM format, and users can enable the WORM feature on existing tapes. Quantum's DLTIce software option puts an unalterable electronic key on each tape to ensure that data on the tape can't be altered. Once the key is applied to the tape, data may be written or appended to the tape, but not deleted or overwritten. The main downside to this approach is the lack of a WORM option for older DLT formats like DLT VS160 or SDLT 320. It may also be more difficult to keep track of how many tapes are reserved for WORM in your environment because WORM data and normal data are both stored on the same type of tape.
Other tape formats require special WORM-enabled tape cartridges. Users of Sun's 9840, 9940 and StorageTek T10000 tape formats need to purchase tapes with its StorageTek VolSafe option; these tapes may be used in any of Sun's tape drives, assuming the drives have the proper microcode to use the VolSafe option. LTO tape users may face a double whammy as only LTO-3 tapes support WORM; in addition to needing special WORM tapes, users may also need to upgrade to LTO-3 tape drives.
MIC and RFID
Vendors are starting to use memory in cartridge (MIC) chips and RFID tags more frequently, but these technologies come with their own issues. Almost all super tape cartridges contain MIC chips, except the DLT/SDLT families. While MIC chips are used primarily by tape libraries to track the location and placement of tape cartridges, in the future MIC chips will be used by applications for data classification, data searching and retrieval. However, the use of MIC chips today is limited by the lack of standards that define what data they contain and how that data should be stored in the cartridge.
Another concern is possible damage to the MIC. Although the possibility of damage is low, MICs can potentially store information such as tape indexes, WORM data, user data-access permissions, barcodes and media partitions. If the chip fails or is accidentally destroyed, the loss of data about the contents of the tape cartridge could be very troublesome.
RFID tagging is another technology whose promise is still unfulfilled; only the StorageTek T10000 includes this technology in its cartridges. Widespread adoption of RFID tags attached to tape cartridges may be driven by tape-vaulting companies such as Iron Mountain Inc., which are beginning to use RFID to track the shipment of tapes to and from user sites.
Tape remains a viable medium for long-term data storage and archiving. Yet as tape capacities and data transfer rates grow, and interoperability with previous generations of tape isn't always a given, some users may find that the latest generation of faster and fatter tapes is overkill for their environments. Before jumping to the next generation, carefully consider whether you need MICs, WORM and the additional capacity. For some applications and environments the answer may be "Not now."