Western Digital finally spun a terabyte up to 7,200RPM last month with the Caviar Black. With three 334GB platters backed by 32MB of cache and a five-year warranty, the Black is well equipped to compete with other terabyte offerings. This latest Caviar may not be the fastest drive on the block in a synthetic throughput drag race, but with the exception of the 10K-RPM VelociRaptor, it's the fastest all-around drive on the market across common desktop applications, real-world file transfers, disk-intensive multitasking, and demanding multi-user loads.
The Caviar Black's strong multitasking and multi-user performance make the drive particularly attractive for workstations and servers, but that's enterprise territory, where single-drive implementations tend to give way to multi-drive arrays. Desktop drives can certainly be used in RAID; however, they're not optimized to handle the error recovery quirks and additional environmental vibration associated with multi-drive arrays.
To address these enterprise challenges, Western Digital has birthed a new RE3 hard drive based on the Caviar Black. As one might expect, this third-generation RE is equipped with all sorts of RAID-specific features and firmware tweaks, but can it live up to the impressive performance standard set by its forebear? Keep reading to find out.
Caviar for enterprise
At the hardware level, the RE3 is essentially identical to the Caviar Black. Both drives use the same 334GB platters, spin them at 7,200RPM, and share a 300MB/s Serial ATA interface. However, the Caviar Black is only available in capacities between 500GB and 1TB with 32MB of cache, while the RE3 line adds a couple of lower-capacity models with 16MB caches. We'll be looking at the terabyte RE3 today, and it's only available with 32MB of cache.
|Maximum external transfer rate||300MB/s|
|Sustained data rate||113MB/s|
|Average read seek time||4.2ms|
|Available capacities||250, 320, 500, 750GB, 1TB|
16MB (250, 320, 500GB)
32MB (750GB, 1TB)
|Idle power consumption||5.47-7.8W|
|Read/write power consumption||5.99-8.4W|
|Idle acoustics||25-29 dBA|
|Seek acoustics||29-33 dBA|
|Warranty length||Five years|
Western Digital quotes a 113MB/s sustained data rate for the RE3, which is a good 7MB/s faster than the rated sustained throughput of the Caviar Black. I wouldn't put too much stock into that specification. WD originally claimed a 145MB/s data rate for the Caviar Black, and that's since been revised to 106MB/s. The results of our synthetic throughput and real-world file transfer tests will give us a much better indication of the RE3's sustained read and write rates.
Helping the RE3 keep bits moving is a dual-processor architecture inherited from the Caviar Black. The RE3 also features Western Digital's IntelliSeek just-in-time actuator mechanism, which only moves the drive head as fast as necessary to get it into position for the next data point rather than as fast as possible. IntelliSeek can help to reduce the vibrations caused by a drive head darting back and forth at full speed—an important consideration for tightly-packed RAID arrays.
Too much environmental vibration can knock the drive head off course, slowing performance in the process. Since IntelliSeek can only reduce vibrations rather than eliminate them completely, the RE3 employs Read Ahead Fast Forward (RAFF) tech that monitors both linear and rotational vibration and adjusts the drive head's position accordingly. Western Digital claims that this latest RAFF implementation boosts the RE3's performance by 60% over the previous generation RE2 in "high vibration environments."
To further protect the RE3 from environmental hazards, WD has equipped the drive with a multi-axis shock sensor similar to what you'd find in a mobile hard drive. This sensor is designed to compensate for physical shock rather than vibration, with an eye toward protecting data from a catastrophic head crash rather than maintaining consistent performance through physical trauma. WD's NoTouch technology also makes an appearance in the RE3, moving the drive head completely off the platter when it's not in use.
When deployed independently, hard drives are left to perform error recovery on their own while the rest of the system waits. RAID controllers aren't keen to idle, though, and if a drive takes too long to recover from an error, it's often marked as bad and dropped from the array. To prevent premature ejection from an array, the RE3 features Time-Limited Error Recovery (TLER) that, er, limits the amount of time the drive will be unresponsive while attempting error recovery on its own. If the drive can't recover the error within this limited time span, it simply gives up, deferring error recovery to the RAID controller
Like most enterprise-class Serial ATA hard drives, the RE3 is rated for a Mean Time Between Failures of 1.2 million hours. The drive also receives additional validation testing that isn't performed on the Caviar Black, although both drives are covered by the same five-year warranty.