Product Reviews

Despite strong competition from other tape formats, Sony has continued to vigorously promote the AIT (advanced intelligent tape) format. Seagate made an early foray into this market and received a coveted Recommended award for its efforts with the AIT-1-based SideWinder 50 (see enterprise, issue 51). It released a SideWinder 70 AIT-2 drive in 1999, but shortly afterwards decided to drop its entire range of AIT standalone drives and autoloaders, with the aim of concentrating on technologies such as Travan, DAT and the new LTO (linear tape open) formats that it felt enjoyed broader support.

This leaves Sony in the position of being the only vendor manufacturing AIT-2-based drives, and the release of the TSL-A500C autoloaders shows it's clearly committed to this technology. So what's so special about AIT-2? Helical scanning is the preferred recording technology, and the drives use 8mm AME (advanced metal evaporated) tapes offering a doubling in native capacity over the AIT-1 format to 50Gb. Performance also sees a considerable boost, with native transfer rates rising to an impressive 360Mbytes/min. AIT utilises a feature of the tape cartridge called MIC (memory in cartridge) Phase 2, which consists of a 64Kb Flash memory chip mounted internally and accessed via a five-pin connector. MIC aims to reduce the time spent by the drive in searching for data as it stores information that's normally found on the first segments of the tape. MIC Phase 2 creates up to 64 partitions on the tape that can be accessed independently using address information stored in the chip. This allows the drive to estimate how far to fast forward or rewind the tape when searching for data, and also unload it without having to rewind to the beginning first.

Sony offers internal and external versions, and each has the capacity to store four cartridges for an impressive total native capacity of 200Gb. ALDC (adaptive lossless data compression) is also supported and offers a maximum compression ratio of 2.6:1, so total capacity could be as much as 520Gb. Despite this huge storage potential, the drives are extremely compact as they use a simple transport system. A small magazine, comprising upper and lower compartments, each

For testing I used a dual-Pentium II/400 system with 256Mb of memory, an Ultra2 SCSI hard disk subsystem and a dedicated Adaptec AHA-2940U2W PCI card for the tape drives. I opted to test under Windows NT 4 and Windows 2000, using Veritas Backup Exec 8 and Computer Associates ARCServe 2000. Sony provides an NT driver on its Web site, but this failed to load as it was written for the standalone AIT-2 drive and not the autoloader versions. After we advised Sony of this, it confirmed that this was indeed an incorrect driver and would be removed from its TSL-A500C Web page immediately. Previously, Backup Exec relied on the vendors' drivers before it would recognise a tape drive, but it now comes with its own embedded set of drivers. However, you'll need to apply the bnt80idrv_230139.exe patch from Veritas' Web site to Backup Exec for Windows NT and 2000, otherwise the TSL-A500C won't be recognised as an autoloader and will only operate as a single drive unit. No such problems with ARCServe 2000 though, as it doesn't require any drivers loaded. Under Windows NT 4 and 2000 Server I found the Sony was recognised immediately as an autoloader and the four slots were made available for all backup-related operations.

Although there were no significant differences, the drives delivered the best performance under NT 4 and ARCServe 2000. Securing a 4Gb array of files returned an average transfer rate of 436Mbytes/min while a full tape to disk verification dropped marginally to 410Mbytes/min. Read operations proved to be a disappointment, as restoring 1.5Gb of data levelled out at only 159Mbytes/min. Operating under Windows 2000 Server ARCServe's backup and verification rates drop back to 374Mbytes/min although restore speeds leapt up to 222Mbytes/min. Load speeds for the autoloader mechanism were unimpressive, as running a full slot inventory took almost eight minutes.

The impending release of the new LTO-based tape drives could prove to be a big threat to the AIT-2 format as they're expected to offer far higher transfer rates and greater storage capacity. DLT (digital linear tape) is also a strong competitor and has a very large and very faithful installed base of users. Even so, companies that are looking to invest in a backup technology that offers high transfer rates and plenty of storage for a reasonable price would do well to check out these autoloaders.