I own a data recovery firm. People come to see us after they have lost something valuable. It might be the next great American novel, or last year’s tax return.
The hard drives that store this information are low-priced marvels of engineering and technology. Most people take them for granted and never give them much thought until a problem occurs. Frankly, I am amazed that they work at all, or for as long as some do.
Based upon what our clients tell us, there are some very common misconceptions about the nature of hard drives and the process of data recovery. We thought it might be helpful and interesting to offer our perspective. However, we are a bit like a hospital— we tend to see only “sick” patients. There are millions of other hard drives merrily humming away and doing their job— for now.
The Hardware
If you have read this far, chances are you have seen a hard drive, or at least what one looks like from the outside. Mechanical drives come three basic shapes and sizes. Most desktop computers use 3.5″ drives; most laptops use smaller 2.5″ drives. Other laptops, and most high-capacity portable storage devices (like iPods®), use very tiny 1.8″ drives.
Newer marvels of technology, called solid-state drive, have no moving parts and are less likely to fail if dropped. The mechanical reliability comes at a higher cost and a reduction of speed. These devices are in some laptops, cameras, and other consumer products.
Myth #1
Solid-state drives are immune from failure.
Reality
You might think that an expensive solid-state drive would be immune from failure. You would be wrong, as these can fail prematurely, too.
The capacities of these drives— the amount of data that they hold— ranges anywhere from 20 gigabytes (GB) to 2 terabytes (TB), which is the same as 2000 gigabytes! This is a fantastic amount of information. If a single typewritten page uses about 2K of data, then our “tiny” little 20 GB drive can hold about 100 million pages!
Drive manufacturers are continually pressing to make drives smaller, faster, cheaper, and with higher capacities for a given size. While these are noble goals, sometimes reliability suffers in the process. We say that those who take their chances with the latest technology are living on the “bleeding” edge.
Predicting Hard Drive Reliability
Myth #2
Hard drive manufacturers, in their product specifications, advertise a figure termed MTBF, or mean time before failure. It is supposedly the average time (in hours) that the product works before an incapacitating fault occurs. A typical claim might be 500,000 hours, which translates into more than 57 years!
Reality
We see many drives that fail in less than one year.
MTBF figures are simply guesstimates and extrapolations, which have absolutely no bearing on how long you can expect your hard drive to last. For example, there is no hard drive model that has been in operation for 57 years, and so there is no real field data to determine actual “average” lifetimes.
People always ask us what is the most reliable hard drive. Although we tend to see failure patterns among certain models, we feel that no single drive or manufacturer is head and shoulders about the rest.
Secret #1
The simple fact is that all hard drives fail eventually, and rarely give adequate warning!
Expert Tip #1
Our advice is: get two drives of your choice, and back up your data to both of them. The more places that your valuable data exists, the less heartache (if any) should one of them fail.
Inside of the Sanctum Sanctorum
Mechanical drives have motors, platters, and heads, which exist inside of a sealed, air-conditioned chamber. The simplest drive may have one head and one platter; the most complicated have eight heads and four platters.
For an analogy (for those of us who are old enough to remember), imagine a little tiny phonograph player, the difference being that the drive motor is spinning at 7200 versus 33 or 45 RPM. Instead of a needle contacting the surface, you have a head assembly that rides just above the metallic surface on a tiny cushion of air. Instead of a single needle and record side, you may have as many as four platters with eight heads— one on each side.
Data is stored on the platters, and the heads delicately seek across the shiny surfaces when reading or writing. Special marks or tracks are written to the platter by the factory to tell the heads their position.
Some drives park their heads on a ramp, while others simply reside near the center during periods of inactivity. The drive shown in Figure 1 has its heads parked in a ramp.
When a drive starts and the platter motor reaches the required speed, the heads fly over the platter surface, and an actuator changes their position. The actuator works a little bit like a loudspeaker cone in response to signals that it receives.
Figure 1: Inside of a Failed Laptop Drive
Secret #2
If a hard drive has multiple heads and platters, the circuits and the computer are not fast enough for all to read at once: only one head reads at a time. Therefore, it is necessary for the heads to switch reading from one platter to another.
Let’s say that you have just recorded a long movie to your hard drive. The movie file may be recorded with head #1 first. Then after a few minutes, into the recording, head #2 takes over and reads or writes to a different platter surface. And so forth.
Switching heads in a drive solves one set of problems, but creates new ones for the data recovery process, as we shall describe.
A thorough description of how hard drives work would span hundreds— if not thousands— of pages. Drives use complicated algorithms for error correction, analog-to-digital conversion, and thermal calibration, among many other necessary functions. When you consider the electronic sophistication and mechanical precision that are a part of every hard drive, it is amazing that they can cost less than $100.00.
Myth #3
Some people believe that there is a magic machine for data recovery that will simply read any hard drive platter.
Reality
While there are other technical reasons that would make this task extremely difficult, the fact that a hard drive’s files are spread over multiple platters presents a huge challenge. File pieces would have to be identified and then linked up, like gluing together shards of broken pottery.
The signal that a head receives while floating above a platter rotating at 7200 RPM is tiny indeed, so a preamplifier circuit is necessary to boost it to a useful level. The head and preamp circuit connects electrically to a printed circuit board located on the bottom of the drive. Components on the circuit board manage the entire process, including communicating with the rest of the computer.
A data recovery company will first try to repair a drive’s mechanical, electrical, or firmware flaws before attempting to recover the data. Problems that remain may reduce the quantity or quality of the extracted data.
For instance, suppose that a drive has four heads, but one of them is defective. If data recovery is attempted on the drive “as is”, then a maximum of 75% of the drive’s data can be retrieved. Once the bad head is replaced, then it may be possible to recover 100%.
Drive manufacturers do not sell spare parts for repair. The only source of heads and other parts is another drive that is deemed to be a suitable donor. Sometimes the match must be very close in terms of date of manufacturer, part number, firmware used, etc. There are hundreds, if not thousands of drive models to choose from, and finding a matching drive is often a challenge.
Therefore, recovery of data from a drive that needs physical repair will cost more than a drive that is somewhat operational.
Secret #3
The intricate operations of a hard drive are controlled by software called firmware, which resides on special tracks on the platter called the service area, and sometimes in a small memory circuit on the circuit board. The firmware and the service area are invisible to users; special, expensive equipment is needed to view and work with them.
Here is a partial list of tasks performed by firmware:
- Communicate with the computer.
- Do a self test and stop or start the drive accordingly.
- Position the heads on the media (platters).
- Control the switching of heads and reading / writing of data.
- Manage defects on the drive.
- Compensate head position for variations in temperature.
- Perform error correction.
- Keep a log of problems and other data.
You can see how important this hidden software is. A problem with any of those functions will result in partial or total drive failure.
Secret #4
Each (modern) hard drive is unique.
Modern hard drives are tested or “burned in” at the factory. The platters are tested for defects, and bad areas (the smallest unit is a sector) are kept on a list and marked out and rendered invisible, so that the drive appears to have zero defects. In actuality, some drives have thousands or even tens of thousands of factory defects!
During the testing process, drives are custom tuned for optimum performance. These custom parameters are known as adaptive data, and differ from one drive to the next. Often it means that parts taken from one drive will not work with another, making data recovery more difficult.
What Causes Hard Drive Failure
Many factors will cause or accelerate hard drive failure. Heat is bad; the cooler you can keep a drive, the better. Fluctuating or noisy power supplies can harm drives, as can mechanical shock.
If a spinning drive is knocked or dropped (as in a laptop), the heads, which normally fly a minuscule distance above the media, can slap and self-destruct or leave scratches upon the platter. This is a severe drive failure, which is illustrated in Figure 1. The photograph shows a ring of damage close to the hub. The particles kicked up by a crash can contaminate and kill other heads or lead to more media damage.
When a drive fails with a head crash, a typical symptom is a series of repetitive clicks that can be hard when the drive is started. The clicks occur because the damaged head(s) cannot find the service area of the drive.
If the service area of the platter is also damaged, then recovery may be impossible.
What should I do if my drive has failed or is failing?
Hard drives do wear out with use. They develop bad or unreliable sectors that are normally marked out, without the user’s knowledge. However, the internal maintenance process is not foolproof, and bad sectors may remain. Bad sectors give symptoms include clicking or unusual slowness while copying files, and software malfunction.
Serious failures often occur without any advance warning, although sometimes may be preceded by the same symptoms as bad sectors, chirping noises, or other unusual sounds.
Secret #4
If you think your drive may be failing, the best thing to do is to stop what you are doing and take your drive to a pro who can image, or make a copy of your drive, using special hardware designed for the task. Trying to copy files off without an imager may stress a failing drive to a point where it becomes irretrievably damaged.
Various software programs are designed to diagnose hard drive failures or recover data. If a diagnostic program reveals bad sectors, the came caveat applies: stop what you are doing immediately.
Secret #5
Data recovery programs should never be used on a failing drive, e.g. one with bad sectors; the results may be unpredictable and often harmful. Data recovery programs work well on hard drives with logical, not physical faults, such as accidental formatting, directory damage, etc.
Resist the Temptation…
Expert Tip #2
The amount of time and effort that you should spend trying to recover your own data should be inversely proportional to the value of the data. In other words, if you don’t care about the data on your drive, experiment as you wish. However, if the data is important, consider the services of a data recovery professional.
Competent data recovery can be expensive, but so is the value of the time needed to try to reconstruct the data on a failed hard drive.
Nonetheless, sometimes our customers try to do their own “recoveries”, and usually make matters worse. For example, we had one client who took the trouble to secure a good donor drive for parts so that he could replace the heads. He wisely performed the operation within the confines of a university’s clean room, a special work area that has highly filtered air to prevent tiny or invisible particles from ruining a drive.
Although he did an admirable job for a first attempt, the head swap was not perfect, and there was damage to the platters as well as a failed head. The unfortunate thing is that his failed drive did not need a head swap, and so he got back about 80% of his data, versus 100% had he diagnosed the fault correctly.
Most other experimenters try less extreme measures. Here are some other common myths:
Myth #4
Placing the hard drive in a freezer may fix the drive enough to recover my data. Well, actually this has helped in a few cases. But the chances of killing a drive are much greater than helping it, especially with the precision tolerances of today’s drives. Freezing a drive is asking for disaster.
Myth #5
Maybe my drive just needs a jolt or a sharp tap to put everything back to normal. This myth has some basis with ancient drives, but with today’s products, it will cause nothing but further damage or destruction.
Myth #6
All you have to do to recover my data is to swap the platters into another drive. Platters are swapped only if the motor has failed. Even so, it is an exacting process: if one of the platters shifts even a millimeter relative to another, the prospects of successful data recovery are remote.
Myth #7
If the drive’s circuit board has failed, all I need to do is to swap it with a compatible part.While it is true that the boards of some drive models are interchangeable, simply swapping boards among most modern drives will not work. This is because most circuit boards containadaptive data for a particular drive.
It is no myth that it takes special tools, training, and lots of experience to meet the technical challenges of recovering data from hard drives. If your hard drive has data worth recovering, use a pro to get it back.
Myth #8
You get what you pay for with data recovery; therefore, I should use the most expensive recovery service if my data is quite valuable.
Reality
The equipment required for expert data recovery in hard drive failures is expensive and somewhat standardized. While the techniques and processes used to recover data do vary, they most likely do not vary by the same degree that “advertised prices” vary.
Expert Tip #3
Things to consider when selecting a data recovery firm:
Unfortunately, there are no generally accepted industry standards for the quality or capabilities of data recovery firms. The skills and experiences of data recovery firms range from inadequate to expert. Negligence or incometence can permanently ruin recovery possibilities, although some drives are so badly damaged that they are deemed unrecoverable by anyone.
How can a consumer select a suitable candidate among hundreds of providers? An established reputation along with a reasonable length in business is certainly a place to start. Other cues include:
- Use a search engine on the firm’s name to get a general feeling of the character of a company as well other pertinent information.
- There are local and national consumer rating services (such as Kudzu®) which provide client feedback about services rendered. See what you can find.
- If you already deal with a computer service provider, ask them who they use and why.
- Call a firm and get a feel for integrity and customer service. Beware of companies that quote a wide range of prices for their services without clearly describing reasons for the differences.
- Ask the firm what their success rate is for your drive, and try to gauge if they are being candid and honest. Bear in mind, however, that certain models and failures present challenges to any recovery firm. Note also that historical success rates will not necessarily determine the outcome of your particular recovery.
- Steer clear of any firm that guarantees they can recover your data without qualification or before they have had the opportunity to inspect your drive.
- Endorsement by hard drive manufacturers such as Western Digital® or Samsung® is a big plus.
- Ask how the data recovery company will return your data to you. If you have a lot of data, you probably want it returned on a hard drive instead of stacks of DVDs.
- Ask if the hard drive company images your drive (i.e. makes a copy of the data) before they attempt the recovery. Avoid any firm that does not make an image first. Also, ask them if they use software to make this image, or if they have hardware designed and dedicated to this task. The use of a hardware-based imager is almost always better, but the gear costs more.
- Lastly— and most importantly— go with your gut. A good service provider should do their best to try to answer your questions and to provide excellent and friendly customer service and support throughout the entire process.
