Specifications

WD2001FASS (Caviar Black 2 TB) and WD2003FYYS (RE4) Overview

The new 7200 RPM models shares many of the features present in prior lines:

• IntelliPower™ — GP drives consume less power with slower
  spindle speeds, performance drop is offset by larger caches and higher
  platter densities.
• IntelliSeek™ — Seek speeds can change
  'on the fly', since the heads do not always need to be moved at full
  speed to make it to the data before it rotates past.
• NoTouch™
  ramp load technology — Previously called "IntelliPark".  Drive heads
  take an 'exit ramp' off of the platters instead of landing on the
  platters when the drive is spun down.  You know how the most damage is
  done to your engine when you start it on a cold morning?  This means the drive heads do not have to break stiction each and every time the drive spins up.  The heads are able to leave the ramp and float onto the spinning disk.

• StableTrac™
  — The spindle is supported at both ends instead of only at the bottom,
  keeping the platters more stable during reads and writes.

• Native Command Queuing (NCQ) — The drive can
  reorder groups of reads/writes to minimize overall head movement, and
  therefore increase effective access time.  Beware - this is only
  effective with an AHCI-enabled SATA controller.

• Perpendicular Magnetic Recording (PMR) — Bits
  are aligned vertically instead of horizontally to get more packed onto
  each platter.  Think dominoes (the game, not the food).
• Low
  power spin-up — Lower RPM's mean less power when trying to get to
  target speed.  These drives also accelerate slower during spin-up as to
  draw even less power.
• 64MB cache — Up from 32MB for the Caviar Black models with capacities less than 2 TB.  Increased cache helps boost random access performance at lower spindle speeds.

• Dual
  processors — Introduced with the RE4-GP line, the additional core helps the drive keep track of the added cache and increased throughput streaming off of the head pack.

Here are some features unique to the new 2TB Caviar Black and RE4 series drives (translated, with pictures):

• Dual Actuator Technology — This new head design treats the 'old' electromagnetic actuator as a coarse adjustment, with an added piezoelectric actuator providing fine tuning over an approximate 5 track width.  This also provides nearly instantaneous track-to-track seeks (within the range of the second actuator).

This engineering marvel should increase seek resolution and open the door for even greater densities in future generation drives.

• Anti-disks — Carried from the Caviar Black line to now include the RE4 series, these are uniquely machined static plates mounted between and around each platter.  Their purpose is to optimize airflow along each platter, reducing turbulence and ultimately keeping head flight more consistent.

The topmost anti-disk can be seen above.  Note this photo is of an earlier Caviar Black.

Both units in this review contain 4 500 GB platters and a different head pack.

The RE4 (like all other RE series drives and the VelociRaptor) include these added features specific to their intended usage:

• RAID-specific time-limited error recovery (TLER) — The drive
  limits the 'hang' experienced on a read error in order to avoid a RAID
  controller considering the drive dead / offline.
• Rotary Acceleration Feed Forward (RAFF™) — I've got nothing.  Just kidding.  More on this near the end of the article.
• Pressure Sensors — Help the drive detect sudden pressure changes present in HVAC / forced ventilation environments (i.e. quickly opening the door to an air-tight server rack space).  Since these pressure changes can cause unstable head flight, actions are taken to prevent inconsistent operation during a pressure change event.

• Thermal extended burn-in — RE series drives are manufactured to tighter tolerances and are put through more quality control steps prior to shipment.
• Memory path protection — The data path architecture has been modified to prevent silent data corruption along the internal data buses (i.e. parity bits).

The feature list is getting fairly long, and the once simplistic 'clean' area of these drives is becoming increasingly complex as Western Digital pushes the envelope even further.  Among the feature additions come some changes that are par for the course for 7200 RPM spindle speeds, and finally a bit of a curve ball:

• Idle / Load power consumption is a whopping 8.2 / 10.7 Watts, up from 3.7 / 6.0 Watts for Caviar Green and 3.7 / 6.8 Watts for RE4-GP.
• Spin-up to ready times of both models are rated at 21 seconds, up from 17 seconds of the RE4-GP, 15 seconds of the Caviar Green, and 13 seconds for the smaller Caviar Black models.

There is really no way around the increase in power consumption, as most of this is a result of simple physics — it takes more power to spin those 4 platters that much faster.  Spin up times are in fact slower, but this is by design.  The spindle accelerates at a constant rate as to reduce power supply loading during power-up and wake-up operations.  This makes things easier on the power supply when spinning up a rack full of drives.

Testing Methods

Our tests are a good mix of synthetic and real-world benchmarks. 
PCMark, IOMeter, HDTach, HDTune, Yapt and our custom File Copy test round out
the selection to cover just about all bases.  If you have any questions
about our tests just drop into the Storage Forum and we'll help you out!

Test System Setup

• PCMark05
• Yapt
• IOMeter
• HDTach
• HDTune

• PCPer File Copy Test