Hard Drive Platter Damage (as seen on Reddit)

by PlatterSwapper

A Quick Overview of the Impact of Platter Damage

What Is A Hard Drive Platter?

These are the physical storage location for the user files and folders. Today’s hard drives will house anywhere from 1 to 4 platters depending upon the storage capacity. They are a sandwich of different materials designed to receive, store and subsequently allow the stable read back of the electromagnetic signal that is your data. The platter(s) are rotated by the spindle motor at a constant speed (typically anywhere from 4200 to 10,000 RPM for the most common models).

What Is Hard Drive Platter Damage?

1. Physical damage:

The platter surfaces should look like a perfect blemish-free mirror. You will usually see a small dark ring at the inner edge, this is an area often referred to as the landing zone, where the heads are intended to rest when the drive spins-down (i.e. the disks stop rotating), this is normal and doesn’t represent damage.

platter as it should look, the arrow indicates the landing zone Figure 1. A platter as it should look, the arrow indicates the landing zone

Physical damage is typically caused by either a mechanical failure or the drive itself suffering an impact (and it is surprising how little force is required to cause damage). A typical scenario would be a set of head impacting momentarily with the disk surface (perhaps the drive was subjected to a knock while writing) Figure 2 below shows the typical result:

hard drive platter damage: where the heads have come into contact with the platters Figure 2. The arrows indicate where the heads have come into contact with the platters

Similarly if debris gets inside and reaches the surfaces then it can become trapped between the head and the platter, this will almost certainly instantly destroy the head and gouge a ring similar to those shown above.

Why so much damage so quickly? Consider that in the average hard disk the platter(s) are spinning at 120 revolutions per second under an extremely delicate read/write head which floats on a cushion of air the tiniest fraction of a mm thick above the spinning surface.

Figure 3. is another commonly seen pattern of physical damage:

Figure 3. Patterned platter damage. Figure 3. Patterned platter damage.

While there has been some physical damage akin to that shown in Figure 2, the platters appear to have been exposed to some other hazard. It may be that this drive has been the victim of the infamous (and misguided) “Freezer Trick”.

This is an urban myth “solution” to a struggling hard drive much-touted online. The idea is that cooling the drive in the freezer will magically allow access. Opinion is divided between the small number for whom the trick has worked and the vast silent majority for whom it has resulted in pretty patterns on the platters but no recovered files. It is much talked about but is rather like the lottery in that you only ever hear about the winners and their chances are one in a million! If you believe that cooling might help, and no question- sometimes it can, then by all means try a few fans (if you are really dedicated you can even try homemade Peltier units which can bring down significantly operating temperature). But don’t put it in the freezer.

Is Platter Damage the End of the Road for Recovery?

In a word- probably.

As described previously the heads are so delicate and hovering at so minute an elevation above platter surfaces spinning so quickly that any disruption to the platter surface is effectively a brick wall waiting to impact and wreck the read /write head. Having said that there are occasions when a drive with evident platter damage (and wrecked heads) has had new heads from a donor transplanted and surprisingly there has been access to user data. Usually the only way to be sure is to try it but it must be said that the vast majority of the time if there is evident damage then the chances are that no files are coming back.

So Should I check My Platters?

Absolutely not (unless you have access to a clean room work area). The risk of even tiny particles settling on the platter surfaces if you open a hard drive outwith a clean room environment are extreme. Most recovery companies are reluctant to accept drives that have been opened (i.e. have had their platter(s) exposed) simply because the chances of recovery after this has happened has dropped sharply.

Besides- it isn’t necessary. Most professional recovery services  will let you know if there is platter damage and should give you the option of whether or not you wish to make the recovery attempt.

2. Media degradation:

Over time and with more and more usage the ability of the platter to maintain the electromagnetic signal that is your data wanes (just as a permanent magnet over time will slowly lose its magnetism).

This sort of damage is the cause of unreadable (or “bad”) sectors (every hard disk is divided up into a certain number of sectors, for example a 500GB hard drive will typically have 976,773,163 sectors available to store your files). A sector is essentially the smallest readable area of data, it is 512 bytes in size. All drives have some bad sectors and will develop more over their lifetime, they have a built-in store of spare sectors which they will allocate as bad sectors develop. However this pool of spare sectors is not infinite and once exhausted the total number of usable sectors will start to decline. This can be more of a problem than may initially appear, a single unreadable sector if located in the wrong place can prevent your operating system from starting at all. More typically users will initially notice that the access time is slowing down, often accompanied by an increase in operating noise.

Any professional data recovery company can work around bad sectors and if caught early enough will usually be able to recover a significant amount or even all of the user documents. But ultimately, too much platter damage will render the precious data unrecoverable.

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