With the exception of its slower spindle and some changes to the drive head to tune it for operation with a 10K-RPM platter, the Cheetah NS is mechanically identical to the 15K.5. Those mechanics are designed to work with the extremely high precision required by 15K-RPM spindle speeds, but when you slow the spindle down, precision requirements fall as well. That gives the Cheetah NS precision to spare, which Seagate has channeled to increase the drive's storage capacity. When it's spinning at 15K RPM, the drive is capable of cramming 300GB onto its four platters; at 10K RPM, the Cheetah NS packs 400GB onto those same platters. Even the math works out nicely: for a 33% drop in spindle speed, Seagate gets a 33% increase in capacity.
In addition to increasing storage capacity, turning down the Cheetah's spindle speed also reduces the drive's power consumption. According to Seagate, the Cheetah NS consumes 34% less power at idle and 33% less during normal operation than its native 10K-RPM products. That makes sense because the drive is using smaller physical disks than its native 10K-RPM counterparts, and smaller platters mean less weight to spin.
Seagate says the NS is more reliable than its native 10K-RPM parts, too. The NS's unrecoverable error rate is apparently ten times better than that of the 10K-RPM Cheetah, and its annualized failure rate is supposedly 17% lower.
So the Cheetah NS has more capacity, consumes less power, and is potentially more reliable. But what about performance? Seagate says the drive is 21% faster than its 10K-RPM competition, and with a 3.9 millisecond average seek time and 97MB/s sustained data rate, it beats the Cheetah 10K.7 by 0.7 milliseconds and 17MB/s, respectively. Those performance benefits come courtesy of the NS's 15K.5 internals. The drive is working with smaller platters, confining data to a tighter physical area that's quicker to navigate. Throw in a drive head that's already faster because it's designed for a 15K-RPM platter, and the Cheetah NS should be faster overall than comparable 10K-RPM drives.
Seagate is already shipping the Cheetah NS to partners and expects to have drives in the distribution channel in the third quarter of this year. There's no word on final pricing, though.