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WD's 500GB Caviar SE16 and RE2 hard drives

Desktop or enterprise?

ManufacturerWestern Digital
ModelCaviar RE2
Caviar SE16
Price (RE2)


TODAY, THERE ARE ESSENTIALLY two classes of 3.5" Serial ATA hard drives available to consumers: drives designed for desktops, and those targeted at the enterprise. Desktop drives make up the bulk of the market and tend to favor lower noise levels and faster performance with sequential transfers, while enterprise drives generally have quicker access times, longer warranties, and better performance with multi-user and multitasking loads.

For most folks, picking a desktop drive is the most logical choice. However, PC enthusiasts have long tapped enterprise-class hardware in search of a better performance. In fact, last year we named Western Digital's enterprise-oriented Caviar RE2 the best hard drive of 2005.

Nearly a year after the original's release, Western Digital is back with a 500GB flavor of the RE2 that promises faster performance and lower noise levels than its predecessor. Western Digital has also rolled out a 500GB version of its Caviar SE16 desktop drive that bears a striking resemblance to the RE2, setting the stage for an inevitable and epic comparison. Read on to see whether you're better off with an enterprise RE2 or a desktop SE16 as we test the drives against each other and a dozen of their competitors.

Separated at birth?
Western Digital recently dropped Caviar from the RE2's name, choosing to simply refer to the drive as the RE2. However, our RE2 sample still bears the Caviar moniker, and looking at the drive's spec sheet, it's easy to see why.

  Caviar RE2 Caviar SE16
Maximum external transfer rate300MB/s300MB/s
Maximum internal transfer rate93.5MB/s93.5MB/s
Sustained internal transfer rate70MB/s70MB/s
Read seek time8.7ms8.9ms
Write seek time10.9ms10.9ms
Average rotational latency4.20ms4.20ms
Spindle speed7,200RPM7,200RPM
Available capacities500GB500GB
Cache size16MB16MB
Platter size125GB125GB
Idle acoustics28dBA28dBA
Seek acoustics33dBA33dBA
Idle power consumption8.90W8.75W
Read/write power consumption10.75W9.50W
Command queuingNCQNCQ
Warranty lengthFive years3 years (OEM)
1 year (retail kit)

The 500GB flavors of the RE2 and SE16 are virtually identical. Both use four 125GB platters, feature 300MB/s Serial ATA interfaces and 16MB caches, and boast similar transfer rates. The RE2 does have a slightly quicker read seek time, but only by 0.2 milliseconds. Even claimed noise levels are consistent between the two drives, although the RE2 apparently consumes a little more power. That's odd, because Western Digital actually says that the RE2's firmware has been optimized to lower seek power consumption without degrading performance. We'll have to rely on our own testing to determine which drive really sips less juice.

Given their similarities, it's only fitting that the RE2 and SE16 look alike. And by alike, I mean separated at birth.

Western Digital dresses both in black, which is a refreshing change from the bare metal finish found on drives from just about every other manufacturer. Of course, it's the same shade of black, so you have to closely inspect the labels to determine which is which.

Drives bearing the WD5000YS label are RE2s, while those tagged WD5000KS are SE16s. Pay close attention to those model numbers, because it appears that some online retailers have not. We've seen several retailers incorrectly use Caviar SE16 to refer to WD5000YS drives, although oddly, none appear to refer mistakenly to the WD5000KS as an RE2. When model numbers differ by no more than a letter, I suppose it's easy to make mistakes.

Fortunately, Western Digital has a whole collection of other letters to help differentiate the RE2 from the SE16. Among them are RAFF, MTBF, and most importantly, TLER.

Hard drives typically perform error recovery on their own, pausing for extended periods of time to save data that might otherwise be lost. That works well enough for drives acting independently, but it can be problematic when multiple drives are bound together in a RAID array. RAID controllers prefer to handle error recovery on their own, so they don't want to waste too much time waiting around for a single drive's heroic attempt at solo error recovery.

If a drive pauses for too long trying to recover from an error, it may be tagged as a failed disk and dropped from the array, even if its attempt at error recovery is ultimately successful. To prevent this premature array ejection, TLER limits the amount of time that a drive will pause to recover an error before it resumes normal operation. If the error isn't quickly recovered by the drive, the RAID controller will sort it out. However, if the drive isn't connected to a RAID controller that supports error recovery, data could become corrupted or lost. That's why Western Digital doesn't recommend TLER-equipped drives for non-RAID applications.

Since it's designed for multi-drive RAID environments, the RE2 naturally supports TLER. Drives even ship with it enabled, although Western Digital says the feature can be disabled by end users. Users can avoid TLER completely with the Caviar SE16, which doesn't support the feature.

In addition to its lack of TLER, the SE16 also misses out on the RE2's support for Rotary Acceleration Feed Forward (RAFF), which detects rotational vibration and adjusts the drive head accordingly. RAFF isn't particularly necessary for single-drive systems, but it's considerably more useful in RAID environments where multiple drives are tightly packed together.

Cramming multi-drive RAID arrays into rackmount server chassis generally puts drives into an environment with higher temperatures and vibration levels than the average desktop PC. That doesn't bode well for a drive's longevity, but Western Digital is confident enough in the RE2's robustness to give it a mean time between failure (MTBF) rating of 1.2 million hours. Unfortunately, Western Digital won't disclose the MTBF of the SE16, saying only that it's in line with other desktop drives. Desktop drives typically have a 1-million-hour MTBF.

Given its longer MTBF rating, it's only fitting that the RE2 is covered by a longer warranty than the SE16. The RE2 is covered for five years. The SE16 gets one year of coverage when sold in a retail kit or three years when sold as a bare drive. Five-year warranties are commonplace for enterprise hard drives, and so are three-year warranties for desktop drives. However, it's a little odd to see the SE16's warranty coverage drop to a single year when the drive is sold as a retail kit. Perhaps Western Digital is banking on retail customers not being savvy enough to compare hard drive warranties in the aisles of Best Buy. Enthusiasts should know better, and since we tend to buy bare drives rather than retail kits, we shouldn't end up with the short end of the stick.