Important Factors for a Successful Head Disk Assembly Swap

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We recently performed a successful data recovery operation for a multinational bio-tech company based in south-west Ireland. In one of their laboratories, there was a desktop PC which experienced hard drive failure. Recently, their laboratory staff noticed the system getting slower and less responsive to use. Last week, it shut down on them and would not successfully boot-up again. They thought they had a full back-up of their files, but on further investigation, it transpired that their backup was a few months out-of-date. Their own I.T. administrators tried to extract data from it, but to their dismay, they heard “click-of-death” sound the moment they connected it to another PC.

The client had used our data recovery service successfully before. They sent us the drive – a 3.5” 2TB Seagate Barracuda S-ATA drive. Our diagnosis revealed that it had 6 failed heads and also showed a lot of evidence of overheating. The increased temperatures which Ireland experienced this July probably did not help.

A head disk assembly swap is perhaps one of the most intricate data recovery operations to perform. It requires excellent theoretical knowledge of the workings of a magnetic hard drive, specialised data recovery tools, a Class-100 clean room, years of experience, patience and a steady hand! The recovery went smoothly and was a complete success. One hundred percent of their data was recovered.

Like any process, there are a number of factors which make the difference between a half-baked recovery and a recovery which is a complete success. For a head disk assembly swap, there are a number of variables which a competent data recovery technician will observe.

Firstly, the technician must acquire an exact-match donor part. For example, in this case, we already had an exact-match head disk assembly part (from an identical 1TB Seagate drive) in stock. This saved the client (and us) time. The part matched the original drive’s model number, revision number and both were manufactured in the same month and year.

The old drive heads should be removed carefully from the donor drive using the proper tools. The head disk assembly should be removed from the platters of the old drive without it actually touching them. In this case, we used a special spacer tool (customised for Seagate data recovery) to carefully remove the head disk assembly from the donor drive without any platter contact. Likewise, the old faulty heads were removed from the drive needing recovery using a similar process.

Alignment of the new head-stack must be in an identical position as the old one. If the HDA is off-kilter, this excessive head-to-platter “eccentricity” cannot be tracked out by the drive’s servo.

The centre of the platters should line up with one another perfectly. This can be helped by using platter alignment tools, but technician experience will be an even greater asset for a perfect alignment.

Lastly, it is very important during this type of data recovery operation that the donor head disk assembly is properly torqued. If not enough pressure is applied, the heads will be at a “flying height” that is either too low or too high. Heads that are flying too close to the platters risk touching, or worse still, scouring them. If the heads are too high the read signal will be too attenuated for the drive’s pre-amplifier, and little or no data will be readable.

There are a lot more issues involved in a head stack replacement which go beyond the scope of one blog post. Technical processes and other minutiae of a recovery operation account for little if there are no results. The most important aspect of the data recovery process is the final outcome. In this case, the bio-tech firm got all their data retrieved and it was extracted and delivered to them on an external USB drive.