Recovering data from a disk with a stuck arm…

Recovering data from a disk with a stuck arm… Data Recovery Ireland

A customer recently contacted us. The had a 4TB WD My Passport USB (wdbyft0040bbl) external drive which they accidentally dropped. When they connected the drive to their PC, they could hear a noise sounding as if the “drive arm” was stuck.  They asked us “maybe if I just opened up the drive and moved the arm that sounds stuck. Do you think that would work?”. The customer’s query was totally understandable. Because let’s face it losing data is not a pleasant experience. And most users just want to get their data recovered quickly.

Is it safe to open up my hard disk with a stuck head?

As you can imagine, opening up a hermetically sealed hard disk drive “to fix a stuck head” is not a good idea for a number of reasons. First of all, there is the issue of dust. When you open up a hard disk, no matter how clean your home or office environment is, dust will start contaminating the platter surfaces very quickly. If you don’t believe this, just get a handheld mirror, wipe the surface clean and then leave it on a table for ten minutes. Unless you happen to live inside a filtered-air laboratory or in a space capsule, you’ll very quickly see specs of dust that have accumulated on the surface of the mirror. Secondly, after an incident such as an accidental disk drop there is a high chance that the disk heads are damaged. And by simply opening up a hard disk to “move the arm” is unfortunately not going to solve that.

The disk-heads are the tiny components mounted at the end of the disk-head assembly which read the data from the platters. Usually, when an external hard disk such as a WD My Passport disk suffers an accidental fall, these heads often get damaged in the process. This makes them unable to read data. And unfortunately, one more deformed disk-heads can also transform into some rather nasty platter scrapers.


Recovering data from a disk with a stuck arm… Data Recovery Ireland
Fig 1 – The raw signal read by the read/write disk-heads is amplified before being send to the Read Channel. The latter then sends the positioning information to the disk controller.

Disk-heads play another crucial function besides just reading data 

But these disk-heads play another crucial role inside your disk. They help position the head-disk assembly (or actuator arm) to be at the right location at the right time just when you need to access a particular file or folder. This is precision engineering at its best. In fact, there is probably no other device in your home or office where an orchestra of precision engineering, electronics and digital signals processing technology converge to perform what superficially seems like a very simple task. Think about that the next time you open up an Excel file…

Recovering data from a disk with a stuck arm… Data Recovery Ireland
Fig 2 – The servo sectors play a pivotal role in the positioning of the disk-heads.

Disk-head positioning information is calculated by the read channel IC by using two variables – track address and servo-burst patterns. There are thousands of concentrically aligned “tracks” on your disk’s platters. At a particular location on the platters, the disk-heads could be reading or writing data. This is known as the track address or Track ID. The Track ID is detected by the disk-heads, sent to the pre-amplifier and then to the read channel IC. Track address alone however is insufficient to give a really accurate position of the disk heads to the read channel IC. This is where servo burst patterns come into play. These are patterns interleaved with the user areas on the platters. They are like road-markings on the platters which indicate to the disk-heads what position they are at. While a lot of people think that a disk out of the factory is blank, its platters already come with firmware information in the System Area and servo burst information between the User Areas. For HDD manufacturers, the process of writing servo-burst information to hard disk platters is actually very complicated. The task requires a special servowriter consisting of a laser interferometer for radial positioning and a clock head for phase information.   

MacGyver fixes to move stuck but damaged disk-heads to another portion of the platter can make the problem even worse.   

When a magnetic hard disk is powered-on (initialised), its heads go into seek mode looking for data track or servo burst data. In a healthy hard disk drive, this only takes a few seconds. However, if you try to manually “lift” a damaged actuator arm off the platter onto another location in the hope that the disk will spin up normally again – you could risk incurring even more damage. MacGyver “fixes” to move a stuck actuator arm to another portion of the platter can make a “stuck arm” problem even worse.

Why moving the actuator arm after a fall often wont fix your disk

Healthy disk-heads are normally meant to skate above the platter surface on a cushion of air. However, damaged disk-heads have the potential to scour sections of the platter surface which were previously healthy. That’s the very last thing you want happening.

In this particular case, luckily the user eschewed the temptation to open up his WD My Passport disk and do a MacGyver on his disk. Instead, in our clean-room, we removed the disk-head assembly (on which the heads are mounted) and replaced them with an exact-match donor replacement. This is a tricky process because all the disk heads (in this case there were 6) must align perfectly with the platters. Then, there is always the probability that the disk might reject the new disk-head assembly. In order to prevent this, we use a highly specialised hardware disk imaging device. This can image a disk at extremely slow speeds (as low as 10 kB/s) and read sector sizes in really small increments (such as 32-byte sectors). At the end of the data recovery process, all the effort was worth it. All of the client’s photos and documents were successfully recovered. These were presented to the client on a brand new external hard disk drive. A disk which he promises he’s never going to drop…

Drive Rescue Data Recovery offers a full data recovery service for accidentally dropped disks. Is your disk making a ticking noise? Does the “arm” of your external hard drive sound stuck? Do you need to fix an external WD or Seagate drive with a stuck arm? We can help recover your precious data. Common models we recover from include WD My Passport 4TB, WD My Passport 2TB (WDBYFT0020bbk), WD My Passport Ultra, WD My Passport for Mac, WD Elements 2TB, Seagate Ultra Touch, Seagate One Touch (STKC4000402), Seagate Expansion Portable, Seagate Backup Plus, Seagate Basic (STJL2000400), Adata HV300 and LaCie Rugged Mini. Call us on 01-485 3555.