Some interesting things are revealed here. Thanks to smaller platters
, Seagate's rated access time
(ignoring overhead) for the Barracuda 18XL equals its specified 5.8 millisecond seek time
plus a 4.2 millisecond latency
that exists for all 7200rpm drives... an access time of approximately 10 milliseconds. The Quantum Atlas V, with its 7200rpm spindle speed
and a 6.3 millisecond seek time, features a specified access time of 10.5 milliseconds, a full half millisecond difference in Seagate's favor.
Interestingly, however, the Atlas V soundly defeats the Barracuda 18XL when it comes to access time, by 1.6 milliseconds. When considering overhead, the Atlas V actually beats its own specified seek time by perhaps half a millisecond, while the Barracuda turns in a figure that we'd expect from a drive pushing 7 milliseconds in the seek domain.
The smaller platters found in the 'Cuda hint that the sequential transfer rate in the outermost tracks will be a bit lower than a drive that features full-sized platters such as the Atlas. This does indeed turn out to be the case. While the Atlas V manages to pull 29 megs a second off of its disks in its outermost zone, the Seagate drive manages a bit less than 27 MB/sec. As we've outlined in previous articles, however, sequential transfer rates' influence is important in a minority of applications.