Best way to recover data from a WD Caviar Blue Hard 3.5” S-ATA Disk

The introduction of the “Caviar” range of hard disks by Western Digital in 1990 proved to be a real step change for electro-mechanical hard disks. This range of disks introduced, the then novel, concept of embedding servo (head positioning) information on the data tracks. But, even more importantly, this range of disks eschewed actuator arms powered by a stepper motor in favour of arms powered by a voice coil motor (VCM). Other disk manufacturers would soon emulate WD’s innovative lead.

Disks need servo information to correctly align the actuator arm (on which the read/write heads are mounted) to the data tracks. Up until then, most manufacturers stored most of their servo data on the disk’s ROM or NVRAM chip. However, storing it on the data tracks meant that the positioning information could be more easily modified or tuned during a production run resulting in more reliable disks less prone to non-repeatable run-out (NRRO) errors.

As already mentioned, the Caviar range introduced electro-mechanical disks which used voice coil motors instead of stepper motors to power and control the disk’s actuator arm. This motor type greatly constrained the number of tracks which the actuator arm (and hence heads) could reach. (Typically, the diameter of the motor casing determined the number of tracks which the head-disk assembly could reach). The continuous variable voltage of voice coil motors along with magnetic hysteresis-free operation resulted in more precise (disk) head-to-platter positioning capability.  This component also gave disk manufacturers the ability to almost double their drive capacities overnight.  

Every year in our Dublin-based data recovery laboratory, we recover from a substantial number of WD Caviar Blue 3.5” HDDs of varying capacities, such as 320GB (WD3200AAKX), 500GB, 750GB (WD7500AZEX), 1TB, 1.5TB (WD15EADS, WD15EARS), 2TB and 4TB(WD40EZRX). While Caviar Blue is Western Digital’s disk for standard uses such as general desktop computing. The Caviar family is also served by the WD Caviar Green line up of disks which are designed for slower speeds (5,400RPM) and quieter operation. While WD Caviar Black models are designed for performance (7,200RPM) and superior caching.

Like with any family of hard disks, there are a number of hardware, firmware and electronic failure modes which can affect Western Digital Caviar hard disks.

Corrupted firmware / damaged System Area (such as damaged translator, G-List, P-list etc.)

Seized or failed spindle motor – A hard disk has a second motor inside it to rotate the platters. Typically, this rotates at 5,200 RPM for Caviar Green, 7,200 RPM for Caviar Blue and Caviar Black.  

Printed Circuit Board Failure (e.g. failed diodes, resistors, etc.,) – This can fail due to over-voltage events. For example, a power surge or accidental liquid spillage can cause a PCB to fail.

Motor Controller Chip – A very common problem with WD Caviar disks is motor-controller failure. This occurs when the motor-controller (typically a Smooth chip) burns out. This can usually be attributed to an over-voltage event happening to the disk.

Pre-amplifier Chip failure – On the underside of a head-disk assembly there is a tiny chip (colloquially known as the “pre-amp”) which amplifies the read/write signals from the head. This component is extremely sensitive to sudden voltage changes. It can fail if the disk experiences a power surge or a liquid ingress event.  

Bad Sectors – While the level of quality of platters used in WD Caviar disks is relatively high, bad sectors can result in your disk failing to boot an operating system or your disk having inaccessible data when connected to a host.

Disk-Heads – Malfunctioning or failed disk-heads are a very common problem. Some disk-heads can malfunction due to wear-and-tear. In other instances, disk-heads on WD Blue Caviar HDDs can fail due to the disk suffering impact damage from an accidental fall. This often results in your WD disk making that dreaded clicking or knocking noise.

Platter damage – This is the often the worst and the most catastrophic type of failure. Platter damage means that even if the disk’s head-disk assembly is changed, most the of data will still be inaccessible. A lot of users ask us why this occurs. Disk-heads traverse along the platter tracks to read, write and erase data. This movement is extremely precise and even a speck of dust can knock the disk-heads off course. So, when the disk-heads meet a section of the platter which is damaged (due to a scratch or notch), they immediately get “derailed”. The means that the head-disk assembly (HDA) can no longer read the data. And even if you replace the HDA with a new one, the same fate will be suffered. In fact, it’s similar to a train trying to traverse a piece of rail track which is buckled. The train might be in perfect condition, but as soon as it reaches the buckled track, it too gets derailed. The same phenomenon happens with disk-heads reading damaged platters except on a more microscopic scale.