June 11th, 2007 by eugene
Western Digital Scorpio WD2500BEVS
The firm first wet its feet with the Scorpio WD800VE, an offering that competed against other players established at the 80-100 GB/platter mark. Shortly after, WD followed with a 120 GB unit and eventually the 160 GB WD1600BEVS, the manufacturer's first drive to incorporate perpendicular magnetic recording (PMR) techniques. While the 160-gig drive matched the capacity offered by competing drives such as the Hitachi Travelstar 5K160 and Seagate Momentus 5400.3, WD's offering more often than not trailed others in StorageReview's key performance tests.
Now WD steps up to the plate once again with its fourth-generation Scorpio WD2500BEVS. The company claims that this latest Scorpio is the first 250 GB 2.5" drive to ship in volume. The drive features second-generation PMR techniques to pack 125 gigabytes across each of its two platters to achieve its impressive capacity. WD specs the drive with a 12 millisecond seek time and equips it with an 8-megabyte buffer.
The WD2500BEVS debuts the manufacturer's "IntelliSeek" technology, a just-in-time style approach that aims to minimize power draw. As we all know, today's hard drives feature rotating platters upon which hundreds of millions of individual sectors rest. In typical non-streaming use, data from a relatively small gathering of sectors is retrieved/written before the actuator then moves to the next group. Previous drives would maximize acceleration and deceleration of the actuator to get the read/write heads in place as quickly as possible.
Under the IntelliSeek paradigm, the drive moves the actuator just fast enough to get to the appropriate track as the target sector(s) approach the heads' location. This minimizes power draw with no hit to performance since the drive would have to wait until the appropriate data location rotated under the heads regardless of when the heads arrived in position. An analogy: Consider an 11am hotel checkout and 1pm flight check-in. A traveler must leave the hotel by eleven and arrive by one, but can minimize the gasoline used by driving slowly… whether he gets to the gate by 11:30 or 12:59, he still boards the same flight and gets to his end destination at the same time.
Though it features a 5400 RPM spindle, the WD2500BEVS in effect represents Western Digital's capacity and performance offering since the firm does not currently market a 7200 RPM line. As a result, in addition to contrasting the latest Scorpio with previous-generation 160GB units, we will also include 7200 RPM drives in the mix:
|Hitachi Deskstar 5K160 (160 GB)||Previous-generation competing unit|
|Hitachi Deskstar 7K100 (100 GB)||Previous-generation competing 7200 RPM unit|
|Seagate Momentus 5400.3 (160 GB)||Previous-generation competing unit|
|Seagate Momentus 7200.2 (160 GB)||Previous-generation competing 7200 RPM unit|
|WD Scorpio WD1600BEVS (160 GB)||Predecessor to the review drive|
For diagnostic purposes only, StorageReview measures the following low-level parameters:
Average Read Access Time- An average of 25,000 random read accesses of a single sector each conducted through IPEAK SPT's AnalyzeDisk suite. The high sample size permits a much more accurate reading than most typical benchmarks deliver and provides an excellent figure with which one may contrast the claimed access time (claimed seek time + the drive spindle speed's average rotational latency) provided by manufacturers.
Average Write Access Time- An average of 25,000 random write accesses of a single sector each conducted through IPEAK SPT's AnalyzeDisk suite. The high sample size permits a much more accurate reading than most typical benchmarks deliver. Due to differences in read and write head technology, seeks involving writes generally take more time than read accesses.
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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With an average access time of 18.1 milliseconds (ms), the WD2500BEVS regresses a bit when contrasted with its 160 GB predecessor. Accounting for the 5.6 ms of rotational latency associated with a 5400 RPM spindle speed leaves the latest Scorpio with a measured seek time of 12.5 ms, a figure half a millisecond above WD's claim.
Packing 125 gigabytes per platter, the WD25000BEVS leverages great linear density to turn in an outer-zone transfer rate of 58.2 MB/sec, nearly 10 MB/sec higher than that of the 160-gig Scorpio. WD's latest trails the 7200 RPM Momentus 7200.2 by just 6%. Rates decay across the Scorpio's tracks and bottom out at a still-respectable 33 MB/sec.
It is important to remember that access time and transfer rate measurements are mostly diagnostic in nature and not really measurements of "performance" per se. Assessing these two specs is quite similar to running a processor "benchmark" that confirms "yes, this processor really runs at 2.4 GHz and really does feature a 400 MHz FSB." Many additional factors combine to yield aggregate high-level hard disk performance above and beyond these two easily measured yet largely irrelevant metrics. In the end, drives, like all other PC components, should be evaluated via application-level performance. Over the next few pages, this is exactly what we will do. Read on!
StorageReview uses the following tests to assess non-server use:
StorageReview.com Office DriveMark 2006- A capture of VeriTest's Business Winstone 2004 suite. Applications include Microsoft's Office XP (Word, Excel, Access, Outlook, and Project), Internet Explorer 6.0, Symantec Antivirus 2002 and Winzip 9.0 executed in a lightly-multitasked manner.
StorageReview.com High-End DriveMark 2006- A capture of VeriTest's Multimedia Content Creation Winstone 2004 suite. Applications include Adobe Photoshop v7.01, Adobe Premiere v6.5, Macromedia Director MX v9.0, Macromedia Dreamweaver MX v6.1, Microsoft Windows Media Encoder 9.0, Newtek Lightwave 3D 7.5b, and Steinberg Wavelab 4.0f run in a lightly-multitasked manner.
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Achieving 467 IO/s per second (IOps) in StorageReview's Office DriveMark 2006, the Scorpio WD2500BEVS manages to tie Seagate's Momentus 7200.2 with the highest score recorded from a notebook-oriented drive in this measure of multi-tasked productivity applications.
The WD2500BEVS slips somewhat in the High-End DriveMark when contrasted with Seagate's powerhouse. Even so, at 377 IOps, the newer Scorpio manages a meaty 20% improvement over the WD1600BEVS. This showing slides the Scorpio past Hitachi's Travelstar 5K160 as the fastest 5400 RPM drive yet tested in this measure.
Three decidedly different entertainment titles cover gaming performance in StorageReview's test suite.
FarCry, a first-person shooter, remains infamous for its lengthy map loads when switching levels.
The Sims 2, though often referred to as a "people simulator," is in its heart a strategy game and spends considerable time accessing the disk when loading houses and lots.
Finally, World of Warcraft represents the testbed's role-playing entry; it issues disk accesses when switching continents/dungeons as well as when loading new textures into RAM on the fly.
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At 402 IOps, the WD2500BEVS improves upon its predecessor by a margin of 12% in our FarCry disc access trace. Though a welcome improvement, the mark nonetheless places the Scorpio near the rear of the pack – 160 GB 5400 RPM drives from Seagate and Hitachi outperform WD's 250-gig unit here.
The Sims 2 treats WD's latest a bit better. 483 IOps allows the WD2500BEVS to push past the 455 IOps turned in by other 5400 RPM units and places it just behind 7200 RPM units.
When it comes to our World of Warcraft trace, the 250 GB Scorpio improves upon the 160 by 18%. While the resulting 328 IOps doesn't quite match scores from Hitachi and Seagate, WD is left trailing by a relatively thin 4% margin.
Unlike single-user machines (whether a desktop or workstation), servers undergo highly random, non-localized access. StorageReview simulates these multi-user loads using IOMeter. The IOMeter File Server pattern balances a majority of reads and minority of writes spanning requests of varying sizes.
IOMeter also facilitates user-configurable load levels by maintaining queue levels (outstanding I/Os) of a specified depth. Our tests start with the File Server pattern with a depth of 1 and double continuously until depth reaches 128 outstanding I/Os.
Drives with any sort of command queuing abilities will always be tested with such features enabled. Unlike single-user patterns, multi-user loads always benefit when requests are reordered for more efficient retrieval.
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Equipped with the SATA interface and accompanying command queuing capability, the Scorpio WD2500BEVS sets itself apart from older drives featuring the legacy 44-pin ATA-100 interface when faced with the concurrency common in multi-user applications.
Interestingly, likely due to the 250 GB drive's higher average access times, the newest Scorpio trails its predecessor by a few IOps at all queue depths.
Noise and Power Measurements
Idle Noise- The sound pressure emitted from a drive measured at a distance of 3 millimeters. The close-field measurement allows for increased resolution between drive sound pressures and eliminates interactions from outside environmental noise. Note that while the measurement is an A-weighted decibel score that weighs frequencies in proportion to human ear sensitivity, a low score does not necessarily predict whether or not a drive will exhibit a high-pitch whine that some may find intrusive. Conversely, a high score does not necessarily indicate that the drive exhibits an intrusive noise profile.
Operating Power Dissipation- The power consumed by a drive, measured both while idle and when performing fully random seeks. In the relatively closed environment of a computer case, power dissipation correlates highly with drive temperature. The greater a drive's power draw, the more significant its effect on the chassis' internal temperature.
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 Scorpio WD2500BEVS turns in an objectively-measured sound pressure of 39.1 dB/A at a distance of 3 millimeters. Subjective impressions match the measurement; the drive is among the quietest we have ever heard. No frequencies stridently stand out and it is likely the drive would not be heard over all but the quietest of ambient noises. Perhaps a side benefit of the drive's intelligent actuator acceleration, seeks are quite muted, hardly audible over ambient even at close distances.
Though WD touts the 250 GB Scorpio's intelligent seek design, the resulting savings of about 0.1 watts under a full load when contrasted with the WD1600BEVS still leaves the firm's latest unit trailing offerings from Seagate and Hitachi when it comes to power economy.
The WD2500BEVS peaks at 4.9 watts upon initial spin-up, matching the dissipation turned in by its predecessor. It is a figure a little on the high side, bringing up the rear and ending up a full 40% higher than the category-leading Momentus 5400.3.
The StorageReview.com Reliability Survey aims to amalgamate individual reader experiences with various hard disks into a comprehensive warehouse of information from which meaningful results may be extracted. A multiple-layer filter sifts through collected data, silently omitting questionable results or results from questionable participants. A proprietary analysis engine then processes the qualified dataset. SR presents results to readers through a percentile ranking system.
According to filtered and analyzed data collected from participating StorageReview.com readers, the Western Digital WD2500BEVS is more reliable than of the other drives in the survey that meet a certain minimum floor of participation.
According to filtered and analyzed data collected from participating StorageReview.com readers, a predecessor of the Western Digital WD2500BEVS, the Western Digital WD800VE , 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.
The Scorpio WD2500BEVS represents a significant improvement over its 160-gigabyte predecessor. In particular, WD's latest provides outstanding performance under the SR Office DriveMark, a trace drawn from an application suite that represents much of mobile computing's raison d'etre. Also worth noting is the drive's exceedingly quiet operation.
On the drawbacks side of things, the drive's power consumption could be better. Despite the intelligent seeks, the WD2500BEVS improves upon its predecessor only marginally and as a result still does not match the enviable numbers turned in by Hitachi's drives.
Even so, with an MSRP similar to that of a 7200 RPM drive ($200 USD), in key areas the Scorpio offers much of the performance found in today's performance-oriented units combined with an additional 90 GB of storage. It is a unit to consider for those contemplating a new notebook drive that are blessed with a robust budget.