Seagate Cheetah 15K.5

Seagate Cheetah 15K.5 Available Capacities Model Number Capacity ST373455xx 73 GB ST3146855xx 147 GB ST3300655xx 300 GB Lowest Real-Time Price (300 GB): Introduction With the introduction of the Cheetah 10K.7 nearly two years ago, industry-leader Seagate Technology signaled that it believed the future of storage belongs to units featuring a 2.5″ form-factor rather than the traditional 3.5″ chassis that has dominated the industry for well over a decade. As a result, the firm has designated the 2.5″ Savvio as the heir-apparent to the 10K Cheetah; the 10K.7 is the last of its kind. Leaving aside the pace at which this transition is taking place, the Cheetah 10K’s end has left the Cheetah 15K as the workhorse of Seagate’s enterprise drive line and as a result has thrust the 15K into the limelight when it comes to the implementation of the newest capacities and technologies. Two years after the introduction of the 147-gigabyte Cheetah 15K.4, Seagate is again the first to take capacities to the next level with the 300-gigabyte Cheetah 15K.5.

The 15K.5 achieves its watershed capacity through the incorporation of perpendicular recording. Simply put, by turning the bits “vertical” as opposed to “horizontal” (or parallel) when contrasted with the plane represented by a drive’s platter, a significantly higher number of bits can be stored per platter track than with traditional methods. Over the past two years, perpendicular recording has made considerable waves in the media’s coverage of the industry. In truth, however, the theory behind the technology has been around for some time… it is just that other, more conservative methods to effect density increases have provided a path of least resistance. These other avenues have been exhausted, however, and the time to encode data vertically has arrived. It should come as little surprise to most that Seagate was first out the door.

While the technique debuted in other lines such as the Momentus (5400.3) and Barracuda (7200.10), nothing underscores the maturity of the technology than its use in the Cheetah family. Through vertical recording, the 15K.5 squeezes a massive 75 gigabytes of data onto each of its four diminutive 2.6″ platters. Seagate specs seek time at 3.5 milliseconds and equips the drive with a standard 16 MB buffer. A five-year warranty backs the drive. The drive will initially be available in Ultra320 and Fibre Channel interfaces with SAS to follow.

When testing the previous generation of Seagate’s SCSI drives (Savvio 10K.1, Cheetah 10K.7, and Cheetah 15K.5), StorageReview uncovered significant performance differences when these drives were set to different predefined cache segmentation strategies through Seagate’s Seatools Enterprise utility. The Cheetah 15K.5, however, returns the same scores regardless of whether the utility’s “Performance Mode” setting is toggled on or off. In the tests that follow, however, the older Cheetah 15K.4’s scores are represented by scores when the drive’s PM setting is “off” (in other words, server mode).

As an enterprise-class 15,000 RPM drive, the Cheetah 15K.5 will be compared to these drives in the tests that follow:

WB99 Disk/Read Transfer Rate – Begin– The sequential transfer rate attained by the outermost zones in the hard disk. The figure typically represents the highest sustained transfer rate a drive delivers.

WB99 Disk/Read Transfer Rate – End– The sequential transfer rate attained by the innermost zones in the hard disk. The figure typically represents the lowest sustained transfer rate a drive delivers.

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Featuring a measured access time of 5.8 milliseconds, the Cheetah 15K.5 holds the line when compared with its predecessor. 15K RPM drives average a rotational latency of 2.0 milliseconds; factoring this in leaves the 15K.5 with a measured seek time of 3.8 ms, 0.3 ms off of Seagate’s claim. Writes weigh in with an average of 6.2 ms, shaving 0.1 ms off of the 15K.4’s score.

The Cheetah 15K.5’s outer-zone transfer rate comes in at a staggering 135 MB/sec, easily besting the previous STR record set by Maxtor’s Atlas 15K II and improving upon the 15K.4 by a whopping 48% margin. When considered in the context of perpendicular recording, the huge increase makes sense. With recording elements vertically arranged rather than horizontal (and thus geometrically tangent to the platter’s track), perpendicular recording is the first major technique in some time that yields higher bit-per-track density rather than the previously more easily achieved increase in tracks per inch.

Rates decay relatively rapidly, leaving the 15K.5 at a less overwhelming 82.6 MB/sec by the time the inner zone is reached. Even so, the figure sets a new record.

Seagate’s latest delivers 649 I/Os per second in the SR Office DriveMark 2006, a 12% improvement over the Cheetah 15K.4. While an improvement, the score nonetheless leaves the 15K.5 trailing far behind Maxtor’s Atlas 15K II and Fujitsu’s MAU3147, previous-generation units from two firms that emphasize performance-tuning in single-user as well as multi-user scenarios.

Under the High-End suite, a collection of traces derived from audio/video production and other more demanding applications, the Cheetah 15K.5 actually regresses slightly compared to its predecessor.

Though they do not represent likely applications for a 15K RPM powerhouse, the three entertainment titles outlined above reinforce the Cheetah 15K.5’s multi-user orientation. While Maxtor and Fujitsu monitor and tune for non-server performance, it remains clear that Seagate does not… the modest increases experienced by the 15K.5 over the 15K.4 above likely arises from low-level improvements and/or by ancillary coincidence through other firmware changes.

Overall, the Cheetah 15K.5 succeeds in offering across-the-board performance improvements over the 15K.4 when it comes to the units’ primary target market: multi-user servers. While not dramatic by any means, the 15K.5, regardless of concurrency level, offers a 5% advantage over its predecessor. In addition, the 15K.5 corrects an anomaly in performance that causes the 15K.4 to suffer under certain load/concurrency beyond 32 outstanding I/Os.

Though the 15K.5 bests the 15K.4 by a 5% margin, it nonetheless trails Maxtor’s category-leading Atlas 15K II by about the same margin under all but the heaviest loads. It is only when concurrency hits 32 (a huge load per drive, even for a 15K RPM unit) that the 15K.5 manages to pull ahead of the Atlas.

Startup (Peak) Power Dissipation– The maximum power dissipated by a drive upon initial spin-up. This figure is relevant when a system features a large number of drives. Though most controllers feature logic that can stagger the spin-up of individual drives, peak power dissipation may nonetheless be of concern in very large arrays or in cases where a staggered start is not feasible. Generally speaking, drives hit peak power draw at different times on the 5V and 12V rails. The 12V peak usually occurs in the midst of initial spin-up. The 5V rail, however, usually hits maximum upon actuator initialization.

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The Cheetah 15K.4 weighed in among the quietest SCSI drives around at just 42.8 dB/A. Its successor, unfortunately, can not match such a low noise floor. Objectively-speaking, at 46.8 dB/A. the Cheetah 15K.5 delivers considerably more sound pressure than the older drive. Subjectively, the unit is indeed louder, though the increase comes predominately from an increase in lower- and mid-band frequencies and thus is not terribly offensive to the ear. The 15K.5 does retain a slight advantage overall when contrasted with the acoustic output of drives from Maxtor and Fujitsu.

Seeks are what one would expect from a 15K RPM unit… definitely audible, along the same lines as the 15K.4 and perhaps slightly quieter than the Atlas and MAU.

At 15.5 watts when idle, the 15K.5 is quite power-hungry, and as a result produces a considerable amount of heat. The good news, however, is that a full seek increases dissipation to just 17.6 watts. In the end, of course, Cheetahs should not find themselves in cramped, unventilated cases but rather well-designed chassis constructed with high-power (performance- and current-wise) drives in mind.

The 15K.5’s peak power consumption overall weighs in higher than that of the 15K.4. However, the drive’s 12V peak (which generally occurs when spinning up platters) is actually slightly lower than that of the older drive and in the end may be less taxing on a power supply.

According to filtered and analyzed data collected from participating StorageReview.com readers, a predecessor of the
Seagate Cheetah 15K.5, the
Seagate Cheetah 15K.3
, is more reliable than of the other drives in the survey that meet a certain minimum floor of participation.

Note that the percentages in bold above may change as more information continues to be collected and analyzed. For more information, to input your experience with these and/or other drives, and to view comprehensive results, please visit the SR Drive Reliability Survey.

 
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