A. The primary variables that play into a library and tape format decision are capacity and performance. Sony's AIT-2 has a maximum uncompressed capacity of 50GB. I've seen as much as 125GB squeezed onto a compression-enabled AIT-2 tape. The AIT-2 offers good performance—as much as 7MBps or faster. The tapes are fairly reliable, and AIT technology is well entrenched in the world of archive devices. Given the choice between AIT-2 and Quantum's DLT, I would choose AIT-2.
Super DLTtape and LTO—which is a joint effort from Hewlett-Packard (HP), IBM, and Seagate—are the new kids on the block. These drives promise superior capacity and performance. LTO has a native uncompressed capacity of 100GB, or twice that of AIT-2. I've seen more than 200GB fit onto a compression-enabled LTO mechanism, but that figure is beyond the norm. On average, expect a compressed-to-uncompressed capacity ratio of less than 2 to 1.
LTO performance seems solid. I'm using VERITAS Backup Exec 8.5 on my evaluation LTO drive, and I'm seeing nearly 13MBps, which is about 8 percent better than the performance of the same configuration on my AIT-2 drive. The only real concern is the maturity of the LTO technology. I tend to be conservative about backups—they're simply too important to leave to chance. LTO might prove to be an extremely reliable and quick backup technology, but the jury is still out. Only after mass utilization will we be able to make a clear call on LTO.
Super DLTtape is pushing DLT's existing barriers. DLT is a proven technology, but it's aging. I don't question Super DLTtape's reliability, but I question its longevity in the face of LTO and new emerging AIT standards.
Speaking of emerging AIT standards, AIT-3 will be available soon. AIT-3 will boast capacity similar to that of LTO, but rumors about initial performance numbers say that AIT-3 will be faster than LTO.