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Western Digital's RE2 750GB hard drive

From Caviar to enterprise
— 11:49 PM on September 23, 2007

Manufacturer Western Digital
Model RE2 (750GB)
Price (Street)
Availability Now

PC enthusiasts are famous for poaching enterprise-class hardware for their personal systems. New technologies tend to debut for server and workstation markets first—just look at the latest processor launches from AMD and Intel—and we don't like having to wait for those developments to trickle down to desktop parts. Even after the latest new hotness has a change to percolate through desktop lineups, enterprise-class hardware can still hold the promise of faster performance, better reliability, and longer warranty coverage: a trifecta of goodness that's hard for any enthusiast to ignore.

Of course there's another element to our penchant for enterprise-class hardware: the sense of almost smug satisfaction we get from deploying otherwise button-down business hardware in systems that are tweaked and overclocked to within inches of their lives, most of which are spent playing games. It's much easier to justify spending money on a system you can legitimately call a workstation, too.

Lately, enterprise-class hard drives have become increasingly popular in enthusiast systems. The 10K-RPM Raptor is perhaps the best example of this trend, but not the only one. Western Digital's RE2 line of 7,200-RPM drives has also become favored among enthusiasts for its delicate balance of performance, capacity, and a five-year warranty. And now there's a new one.

Based on a Caviar SE16 750GB foundation that we already know delivers phenomenal performance with low noise levels, the latest RE2 benefits from tweaked firmware, RAID optimizations, more extensive reliability testing, and extended warranty coverage. Read on to see if those extras are enough to elevate this enterprise drive above not only its desktop counterpart, but also the fastest drives on the market.

The drive
Before diving into the RE2, we must first separate it from the desktop Caviar SE16. That's not as easy as one might expect, in part because the drives are cosmetically identical.

The Caviar SE16 and RE2: I can't see the difference. Can you see the difference?

These drives are similar in more than just their appearance, as well. 750GB flavors of the Caviar SE16 and RE2 are mechanically identical.

Only upon consulting the drive's label can we discern between the SE16 and RE2. Drives with model number WD7500AYYS are RE2s, while those tagged with WD7500AAKS are Caviar SE16s.

Making an arbitrary distinction between drives that are mechanically identical seems unnecessary, but there's a method to Western Digital's madness here. One needs only to dig through the drives' specifications to get a hint at where the RE2 starts to differ from its desktop counterpart.

Caviar SE16 RE2
Maximum external transfer rate 300MB/s 300MB/s
Maximum buffer to disk transfer rate 972Mbps NA
Sustained buffer to disk transfer rate NA 784Mbps
Read seek time 8.9ms 8.9ms
Write seek time 10.9ms 9.6ms
Average rotational latency 4.2ms 4.2ms
Spindle speed 7,200RPM 7,200RPM
Available capacities 750GB 750GB
Cache size 16MB 16MB
Platter size 188GB 188GB
Idle acoustics 28dBA 28dBA
Seek acoustics 29-33dBA 34dBA
Idle power consumption 8.40W 8.5W
Read/write power consumption 8.77W 9.5W
Native Command Queuing Yes Yes
Recording technology Perpendicular Perpendicular
Warranty length Three years (OEM)
One year (Retail)
Five years

On the surface, the specs look comparable, as they should be for drives that share 300MB/s Serial ATA interfaces, 188GB platters, 7,200RPM spindle speeds, and 16MB caches. Yet despite all those similarities, there are a few deviations worth noting. The RE2 manages to shave 1.3 milliseconds off the Caviar SE16's write seek time, for example. 1.3 milliseconds doesn't seem like much, but within the confines of a modern PC where bits flip at gigahertz clock speeds, it's actually quite a long time.

A more aggressive algorithm may make the RE2 seek a little faster, but that optimization is not without cost. The RE2's seek acoustics are at least a decibel higher than those of the SE16, suggesting Western Digital hasn't been shy about optimizing for performance at the expense of silence. That's a sensible trade-off for a drive like the RE2—a single decibel will easily be lost in the droning hum of most enterprise environments.

In addition to running a little louder than its desktop cousin, the RE2 is also rated for higher power consumption, particularly under load. The drive does attempt to cut power use by employing Western Digital's IntelliSeek just-in-time actuator mechanism, though. Rather than darting the drive head back and forth between data points as fast as possible, IntelliSeek takes advantage of the rotational latency inherent to spinning platters and only moves the drive head as fast as necessary to get it into position for the next time the data point is scheduled to come 'round on the platter. Western Digital is adamant that IntelliSeek still gets the drive head into position on time, so while vibration and power consumption are reduced by the slower drive head movement, seek times don't suffer.

The RE2 inherits IntelliSeek from the Caviar SE16, but that's not all. RE2 drives also brings the SE16's SecurePark head parking mechanism, improving the drive's tolerance of non-operational shock. The SE16's StableTrack motor makes its way to the RE2, as well. This motor's shaft is secured at both ends, which Western Digital says improves the drive's ability to withstand environmental vibration.

Environmental vibration is actually a major concern for enterprise drives because they're often grouped in RAID arrays that are packed like sardines into tight enclosures. With that in mind, the RE2 employs a couple of unique features that you won't find in the Caviar SE16. The first of these features is Rotary Acceleration Feed Forward, or RAFF. RAFF uses accelerometers in the hard drive to sense rotational vibration and adjusts the position of the drive head to maintain a safe distance from the platter. According to Western Digital, this feature allows the drive to sustain higher transfer rates in vibration-rich environments.

With an eye towards RAID applications, the RE2 also features Time-Limited Error Recovery (TLER). Hard drives typically perform error-recovery on their own, occasionally pausing for longer periods of time to save data that would otherwise be lost. Those pauses aren't an issue for single-drive environments, but they can be problematic when multiple drives are combined in a RAID array. RAID controllers prefer to be in charge of error recovery, and they can be a little impatient. If a single drive in an array pauses for too long trying to recover an error on its own, a RAID controller may mark the drive as failed and drop it from the array. To prevent this kind of array degradation, TLER reduces the amount of time that a drive will attempt error recovery, ensuring that RAID controllers don't prematurely assume that a drive has gone off the reservation.

In the past, Western Digital has warned against using drives with TLER in single-disk environments. However, no such warning accompanies the 750GB RE2, which WD says can be used all by its lonesome.

With RAFF and TLER, the RE2's enterprise orientation starts to come into focus. And there's one more acronym of importance to tackle: MTBF. Western Digital estimates the mean time between failures for its RE2 at 1.2 million hours, which is typical for an enterprise-class hard drive. MTBF data isn't available for the Caviar SE16, although since it's mechanically identical to the RE2, one would assume that's its reliability is comparable. Western Digital does say that the RE2 receives more extensive testing than its desktop drives, though.

Perhaps that more extensive testing makes it easier for Western Digital to step the RE2's warranty up to five years. Five-year warranties are typical for enterprise drives, of course, but the desktop Caviar SE16 is at best covered for only three years.