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SPECIFICATIONS
The specifications below are specific to the models that we examined. Capacity, cache size, platter number, interface, and even performance vary from
model to model even within a single product line. Acoustics and power dissipation also vary depending on the number of platters
in the drive; smaller capacity drives tend to have fewer platters, and
tend to produce less noise and use less power.
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Manufacturers' Specifications
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| HDD Model |
Western Digital Raptor WD740GD
|
Western Digital Caviar SE WD2500JD
|
| Capacity |
74 GB
|
250 GB
|
| Cache |
8 MB
|
8 MB
|
| Platters |
2
|
3
|
| Rotation Speed |
10,000 RPM
|
7,200 RPM
|
| Interface |
SATA
|
SATA
|
| Latency |
2.99 ms
|
4.2 ms
|
| Average Seek |
4.5 ms
|
8.9 ms
|
| Start/Stop cycles |
20,000
|
50,000
|
| Operating Temperature |
5 - 55°C
|
5 - 55°C
|
| Power Dissipation: Idle / Seek |
7.90 / 8.40 W
|
8.75 / 9.00 W
|
| Acoustics: Idle / AAM seek / normal
seek |
32 / – / 36 dBA (no distance/angle given)
|
28 / 33 / 35 dBA (no distance/angle given)
|
If the SPL specs are for one meter distance, they are not promising at all. One has to wonder if the acoustics data is outdated (perhaps based on their ball bearing versions?), as our results were much better.
WESTERN DIGITAL RAPTOR
Although the Raptor is Western Digital's enterprise class ATA drive, it has found
a niche as a top-performing single-user drive. Its ATA interface makes it attractive
for use in desktop machines but also reduces its usefulness in the server market,
which is dominated by SCSI drives. Additionally, even though a version of command
queuing is implemented in the drive, there are few drive controllers that can
take advantage of it. Command queuing is quite beneficial for to server performance but offers
little benefit to single users.
Western Digital is selling the Raptor on price, performance and reliability. Although expensive
for a SATA-based drive, it is still cheaper than most of the SCSI drives that
it is competing against.
The reliability of the Raptor is a bit of a puzzle. Western Digital offers
a long, five-year warranty for the drive, so they must have some confidence
in the drive, but its start/stop cycle rating is only 20,000 — less than
half of the 50,000 that is standard for 7,200 drives. Of course, because it
is sold an an enterprise drive, it is probably intended to operate continuously
without spinning up or down. The number that Western Digital wants you to look
at is MTBF — Mean Time Between Failure — estimated at 1.2 Million
hours. Unfortunately, it is quite difficult to interpret what this means in
real terms, and it is very difficult to judge just how reliable the drive is
because few other manufacturers specify MTBF for their drives.
One thing to consider is that reliability is correlated to the amount of heat
a drive produces. The casing for the Raptor is heavily ridged, which should
allow it to dissipate more heat than usual. These may be necessary to dissipate
the additional heat generated by its 10,000 RPM spindle speed.
The sides of the raptor are ridged to increase heat dissipation.
WESTERN DIGITAL CAVIAR SE
It's difficult to tell how the Caviar SE compares to other drives by examining
it's "feature" sheet. Not surprisingly, most of the listed features
relate to performance, but it is difficult to read through the trademarked names
and vague descriptions to find out which of them are genuine features and which
are standard on all drives. The ones we are most interested in are related to
noise: WhisperDrive™ and Soft Seek™.
Soft Seek is almost certainly an implementation of AAM that trades a small
amount of seek performance for quieter seeks. Depending on the drive, AAM can
reduce seek noise to near inaudible levels or have next to no effect. We will
be sure to test how this drive behaves later on.
The description of WhisperDrive is a little more obscure. It reminds
me of Intel's Centrino "technology" which names a system
of features, not a single technology. Part of WhisperDrive is probably
the FDB motor that prompted this review, but we have no idea what is meant by
a "highly efficient power driver design" (sure sounds good though).
One feature that does seem to be unique to Western Digital drives is the SecureConnect SATA connector that is supposed to be five times stronger than the standard
SATA connector. We have no idea how Western Digital measured the strength of
the connection, but, given the flimsy quality of most SATA connectors, we welcome
this attempt at improvement. Unfortunately, we were unable to actually test
the connector because it requires a proprietary cable that was not shipped with
our test sample. A close examination of the SATA socket reveals a small hole
to one side of it. Our guess is that the special cable is designed to latch
into this hole to provide a secure connection.
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