Enterprise storage used to be dominated by expensive SCSI solutions with lofty spindle speeds. In recent years, however, Serial ATA drives spinning at a mere 7,200RPM have become increasingly popular for applications that favor storage capacity and cost over performance. It's easy to see why; current SCSI drives top out at only 300GB, and you'll pay more than a dollar per gigabyte for the privilege. Meanwhile, the latest Serial ATA drives manage to pack up to a terabyte of storage into the same 3.5" form factor as their SCSI counterparts, but at closer to 25 cents per gigabyte.
You can't just show up in a server room with a palette of desktop drives, though. Enterprise customers are a discerning lot, and they're particularly, er, particular about reliability, power consumption, and suitability for multi-drive RAID environments. Standard desktop drives simply won't do, which is why hard drive manufacturers have developed SATA drives with enterprise-class credentials. These drives are based on desktop models, but they tend to undergo more stringent reliability testing, benefit from additional features, and come equipped with firmware tweaked to improve performance with demanding enterprise workloads.
Seagate first dipped its toe into the enterprise SATA market with the Barracuda ES, which was based on the company's then-current 7200.10 drive technology. Since then, Seagate has rolled out a 7200.11 drive platform, and with it, a new Barracuda ES.2. With a terabyte of total capacity spread over four 250GB platters and 32MB of cache, the ES.2 looks great on paper. But how does the drive's performance compare with its direct rivals and the 7200.11 on which it's based? Read on to find out.
The Barracuda ES.2 shares the same underpinnings as the desktop 7200.11, which is a pretty good foundation. After all, the 7200.11 boasts 250GB platters spinning at 7,200RPM, a feat unmatched by other enterprise-class terabyte drives. Hitachi's Ultrastar, for example, only packs 200GB per platter, giving the drive head access to less data over the same physical distance as the ES.2. Western Digital's RE2-GP matches Seagate's 250GB platters, but it does so with a spindle speed closer to 5,400RPM, yielding an obvious advantage to the Barracuda.
With the same basic hardware as the 7200.11, it's no surprise that the Barracuda ES.2's specifications are all but identical. Seagate just happens to publish more detailed information on the ES.2 than it does for the 7200.11. There are, however, a few key differences between the drives that are worth highlighting.
|Barracuda 7200.11||Barracuda ES.2|
|Maximum external transfer rate||300MB/s||300MB/s|
|Maximum internal transfer rate||NA||160.9MB/s|
|Sustained data rate||105MB/s||105MB/s|
|Average rotational latency||4.16ms||4.16ms|
|Average read seek time||NA||8.5ms|
|Average write seek time||NA||9.5ms|
|Available capacities||500GB, 750GB, 1TB||250GB, 500GB, 750GB, 1TB|
32MB (500GB, 750GB, 1TB)
|Idle acoustics||2.5-2.7 bels||2.5-2.7 bels|
|Seek acoustics||2.8-2.9 bels||NA|
|Idle power consumption||8.0W||8.0W|
|Seek/typical power consumption||10.6-11.6W||10.6-11.6W|
|Mean Time Between Failures (MTBF)||750,000 hours||1.2 million hours|
|Warranty length||Five years||Five years|
The ES.2, for example, is available as a single-platter 250GB drive, while the lowest 7200.11 capacity is 500GB. There are also differences when it comes to cache; all ES.2 capacities enjoy a full 32MB, but with the 7200.11, 500 and 750GB flavors are also offered with 16MB. Seagate technically makes versions of the ES.2 with 16MB of cache. However, those drives swap a Serial ATA interface in favor of 300MB/s Serial Attached SCSI.
Despite sporting smaller caches, Seagate says SAS-enabled ES.2 drives draw slightly more power than their SATA counterparts. SAS models are rated for idle power consumption of 10.2W, with typical power consumption pegged at 13.0W.
Power consumption is an important metric for enterprise customers looking at running not just one drive, but servers, racks, or even rooms filled with them. To help improve its energy efficiency, the ES.2 features a dynamic power optimization scheme called PowerTrim that can selectively shut down portions of the drive that aren't in use. Seagate says PowerTrim has no impact on overall performance, and given the company's own power consumption specifications, it appears to be implemented in the Barracuda 7200.11, as well. We'll take a closer look at actual drive power consumption a little later to see how the two drives compare.Another focus for enterprise customers is vibration tolerance, and for good reason. When you have multiple drives sandwiched together in the same enclosure, vibrations produced by the mass of spinning platters and seeking actuators make it more difficult for drive heads to stay on track. If vibrations become too severe, drives may interrupt operation to prevent catastrophic head crashes. Such interruptions can degrade performance, which is why Seagate is quick to claim that the ES.2 has the highest rotational vibration tolerance in its class—12.5 Rad/sec² at 1500Hz, to be exact. Interestingly, the ES.2 owes much of its vibration tolerance to firmware tweaks that you won't find in the 7200.11.
The ES.2 also differs from the 7200.11 when it comes to reliability specs. Both drives are covered by a five-year warranty; however, the ES.2 is rated for a mean time between failures (MTBF) of 1.2 million hours—much longer than the 7200.11's mere 750,000 hours. Seagate also says that the ES.2's nonrecoverable read errors per bits read is an order of magnitude lower than that of the 7200.11. That sounds impressive, of course, but an order of magnitude in this case is the difference between 1015 and 1014.We don't usually spend a whole lot of time poring over a hard drive's physical characteristics because there's rarely anything to see. The ES.2's interface speed jumper gives us an excuse for one close-up, though. This jumper controls the speed of the drive's Serial ATA interface, which is set to 150MB/s by default. You'll have to remove the jumper to enjoy SATA in all its 300MB/s glory, and that's easier said than done given how the half-height jumper is recessed in the drive's casing. A pair of tweezers did the trick for me, but a full-size jumper would've made things much easier.
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