Investigation Into Recovery from Seagates

by PlatterSwapper

Tierra’s ongoing research and development program revealed the range of hard disk recovery problems encountered with Seagates. Specialist physical recovery is needed when a hard disk fails and the files and folders become either partially or totally inaccessible. Seagate Technology is one of the world’s largest manufacturers, with 52,000 staff and annual revenue in excess of US$11 Billion. In 2006 they bought out Maxtor, which at the time was itself the worldwarranty page‘s third largest maker of hard disks.

The statistics for this article are based on the case notes from the work carried out on Seagate Barracuda and laptop hard disks received in our labs over the last 6 months.

First some information showing which models we have seen in the labs. Approximately 80% of Seagates were among the 24 models listed in the table below:

Model % of Seagates Received Model % of Seagates Received
ST3500620AS 8 ST3160023AS 2
ST9160821AS 7 ST3250310NS 2
ST31000333AS 5 ST3500830A 2
ST3500320AS 5 ST31000340AS 2
ST3500630AS 5 ST31000528AS 2
ST3500820AS 5 ST3320620A 2
ST3500830AS 5 ST3320620AS 2
ST96812AS 4 ST3500418AS 2
ST3750630AS 4 ST3750330AS 2
ST3250823A 3 ST9100823A 2
ST9320320AS 3 ST9100824AS 2
ST31500341AS 2 ST9250827AS 2

The remaining 20% were composed of the following models:

ST31000340NS ST3200822AS ST3640323AS
ST3250310AS ST3200826A ST3750640NS
ST3500320NS ST3200827AS ST3802110A
ST380817AS ST3250410AS ST380819AS
ST9120821AS ST3250620NS ST9100825A
ST9146802SS ST3250820A ST9120817AS
ST9160412ASG ST3250820AS ST9120822A
ST9160823ASG ST3250824A ST9120822AS
ST94019A ST3300555SS ST9120823AS
ST9500325AS ST3300622AS ST912823ASG
ST980811AS ST3300831A ST9160314ASG
ST3120026AS ST3320613AS ST9160411ASG
ST3160021A ST3320813AS ST9160823AS
ST3160023A ST3360320AS ST9250315AS
ST3160812 ST340014A ST94011A
ST3160812AS ST340016A ST9408114A
ST3160815A ST3400620A ST94813AS
ST3160815AS ST3400633A ST960822A
ST3160828AS ST340810A ST98823AS
ST3184321C ST34572N
ST320011A ST36002A

So, what are the Problems:

Bad Sectors

By far the most frequently encountered problem in Seagates, and this is common to all manufacturers of hard disks is what is referred to as “bad sectors”.

Over time and with heavy usage the ability of the platters (the spinning disks inside that hold the data) to maintain the electromagnetic signal that is the user data wanes (just as a permanent magnet over time will slowly lose its magnetism).  It is however also true to say that we routinely see all types which have been used lightly, are still under warranty and yet are suffering from bad sectors.

This sort of platter damage is the cause of unreadable (or “bad”) sectors (every HDD is divided up into a certain number of sectors, for example a 500GB hard disk will typically have 976,773,163 available for storage). A sector is essentially the smallest readable area on the platter, it is usually 512 bytes in size. All disks have some bad ones and will develop more over their lifetime, they have a built-in store of spares which they will allocate as bad ones develop. However this pool of spares is not infinite and once exhausted the total number usable will start to decline. This can be more of a problem than may initially appear, a single unreadable sector if located in a suitable part 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.

If a hard disk with bad sectors is received early enough (in other words before the they become widely spread) then it is almost always possible to recover. The amount recoverable is entirely determined by how many have already developed.  The greatest enemy is the Windows CHKDSK program. This will often run automatically on boot-up unless prevented and will scatter and over-write the user data in an effort to get back to a condition where the Operating System is working again, but it will happily overwrite user data in the process.

The other great enemy to recovering from Seagates in this condition is recovery software. This will thrash the hard disk in an effort to locate the data, all the time adding more and more bad sectors.

The only sensible approach is to clone all of the accessible parts in an environment that will not change the contents. Once the clone has been obtained then recovery software can be run without making the situation any worse. There are various methods and equipment used to clone equipment in this state. It is also often the case that a drive with problems other than this will also turn out to have bad sectors when those other initial problems have been solved.

Ratio of Drives With Bad Sectors Found In Seagates

From the Seagates that have passed through our labs in the period covered by this article approximately 35% of those received were suffering from bad sectors.

Firmware Issues:

The next most common failing for our Seagate recovery sample was firmware problems.

Firmware is special code stored internally within the device in order to get itself started. It cannot be accessed without specialised hardware. Any professional recovery service will have access to and proficiency in the use of such equipment. It will include (among many other pieces of information):

  • HDD Model
  • Serial Number
  • The location of the storage areas on the platters that will be utilised to store user data
  • Over its lifetime, as individual sectors become unreadable, space lost will be reallocated with new space from a limited bank of spares, the firmware keeps a map of these re-allocations.

To complicate matters this firmware is stored in part on the printed circuit board (usually either on a discrete EPROM chip or else embedded within the PCB processor chip) and in part on the platters. At initial power-up the contents of the PCB firmware store are read, this portion of the firmware will then direct start up, this includes where it will look on the platters for the remaining part of the firmware.

The symptoms exhibited by damaged firmware will vary widely depending upon the exact nature of the firmware damage. On spin-up, it may click repeatedly and not appear in the BIOS or may seem to be detected by the PC or Mac but not allow access to user data. One of the more common symptoms of damaged firmware (especially for Seagates) is spinning-up and sounding normal (that is to say no repetitive clicking from the heads) but simply not appearing in BIOS or appearing but shown as having zero capacity.

Generally speaking, if firmware becomes corrupted the hard disk will fail to initialise. Seagates, just like models from other manufacturers suffer both from such corruption and sometimes from known firmware “bugs” which just like bugs in other software programs crop-up occasionally.

Most of the time, with the appropriate knowledge, experience and technology it is possible to re-build or work around these faults.

Of the Seagates received in the last 6 months, in the region of 15% were affected by one firmware problem or another.


Failed or Weak Read/Write Heads:

Just as the magnetic platter loses its ability to store an electromagnetic signal over time and with heavy use it is also the case that the ability of the heads to read that data can similarly diminish. When recovering from Seagates, such problems can arise through time with age or can be the result of a physical event such as suffering an impact.

The symptoms are typically a heavy clicking heard and felt after the platters have spun-up. In this condition the drive will usually not be identified in BIOS and is very unlikely to get as far as loading an Operating System or file listing. It is important to bear in mind however that many other problems other than failed heads can also cause it to click at start-up.

After eliminating other possible causes of these sounds the usual procedure is to carry out an internal inspection to establish whether there has been any damage to the platters themselves, where this is not the case then a closely matching sacrificial donor would be acquired from which to transplant the read/write heads.  This work must of course be carried out in a clean-area environment.

In instances where the heads have damaged the platter it is usually the case that the damaged area of the platter will wreck the donor heads, it is therefore seldom worthwhile to attempt a head-swap with damaged platters. This is because the heads float on an air cushion the tiniest fraction of a millimetre above the platters which are spinning at typically 5400 or 7200 RPM, as you can imagine, the smallest disruption to the platter surface will impact and severely damage the head.

Our work with Seagates showed a little over 12% of the cases were found to be due to failed or weak read/write heads.

Seized Platter Motor:

The platters inside are spun by the platter motor. If the platter motor becomes seized then the platters will not spin-up. This is usually the result of having being subjected to an impact of some description. It can be surprising how little force in such an impact is needed to seize the platter motor. With Seagates, we have seen more than one instance of an external merely falling onto its side being sufficient.

The symptoms (as you might imagine) are that on application of power there is no spin-up. There is usually some indication of attempts to spin-up, usually a slight vibration every second or so.

There are other causes of these symptoms, for example where the read/write heads have become stuck to the area of the platters, the friction alone can be sufficient to prevent the platters from spinning-up.  Accurate diagnosis, as well as access to a clean area environment are essential in both cases.

Where the cause has been found to be a seized platter motor it is necessary to carry out a platter swap. This is a procedure whereby the platters, printed circuit board and the read/write head assembly are moved to a closely matching donor chassis in order to utilise the donor’s platter motor (which is built into the chassis) in an attempt to access the user data.

Approximately 10% of our Seagates were suffering from seized platter motors.


Printed Circuit Board (PCB) Problems:

The 2 most common problems associated with Seagate PCB failures are:

  1. Over-voltage supply, either through a bad connection or a spike from the PC /Mac power supply.
  2. The failure of the chip on the PCB that controls the platter motor.

In the case of over-voltage supply the path to recovery depends of course upon how much damage has been done. In some instances it is possible temporarily to repair the PCB at least for long enough to recover the user data. In other cases it may be necessary to replace the PCB (which is almost never a straight swap, it almost always involves transferring firmware unique to the individual drive from the old PCB to the new). In many instances the damage may have gone even further, it is common for the so-called pre-amplifier to suffer damage in the event of an over-voltage supply, this is a part of the read/write head assembly inside and will also require replacing if it has been damaged.

In the case of platter motor controller chip failure it is usual procedure to swap the PCB with that from closely matching hard, but as stated above the unique firmware from the defective PCB will almost certainly need to be transferred in order to gain access to the files and folders.

Around 10 % of the Seagates in the sample were suffering from PCB faults.

The remaining 18% of the Seagate sample were essentially intact but had suffered so-called logical damage. That is to say that the device itself was fully operational but the data had been lost due to accidental re-format, deletion or file system corruption.

In this situation the computer will usually boot into the operating system as usual but, of course, the required data cannot be accessed.

Seagate Momentus 5400 With Firmware 7.01 or 3.CAE

These are a rather unfortunate special case. These specific firmware versions (shown on the label as  FW:7.01 or FW:3.CAE) are particularly prone to problems with the magnetic substrate that makes up the storage platters. The surface of the platters appears to degrade much more than other models. For this reason recovery rates for these are very poor compared to other models or families.

A word on Seagate recovery rates:

You will note that we do not give recovery rates in this article for the sample of Seagates under analysis. The reason for this is that recovery rates are essentially meaningless. They are rather like survival rate league tables for hospitals, at first sight they seem to offer a precise and valuable indication of expected outcomes but with closer examination and a little thought are at best misleading.  With any competent, professional recovery company the outcome is essentially determined by the condition of the patient on admission.

As a simple example – if a disk is suffering from bad sectors and a customer requires a particular critical document, then the outcome will be 100% successful if they do not occur in the region of the platters where that crucial document is stored, but may well be 0% if they have affected that particular area.

Giving a recovery rate across all disk drives received simply averages away any meaningful information.

For more information and help on recovering critical files from your Seagate, fill in our contact form or call us on 0845 094 0027.

{ 3 comments… read them below or add one }

andya May 23, 2012 at 4:17 am

hi, i have seagate 1tb sata 2.5″ (laptop) FW-cc94. nowdays it shows aas read/write error when attached to pc/laptop. spins finely n their is not a single mark of burning on pcb. what would be the problem then? from where i can get donor?
plz reply…..

TomRat May 25, 2012 at 1:15 pm

this could be a number of things, ranging from bad read-write heads to firmware issues. If you cannot access the data using your computer or a friend’s computer, it’s time for a professional analysis before you cause any damage. Drop us an enquiry form if you would like us to take a look,

Stype October 31, 2012 at 9:09 am


I have a ST3250820AS, firmware: 3.AAE

It is damaged by the overvoltage (power supply issue).

I also have ST3250823AS, firm: 3.01.

Can I try exchanging the PCB from ST3250823AS to ST3250820AS?

Am I risking anything by doing so ?

Also if I want to transfer the firmware, is it ok to unsolder the FLASH EEPROM chip from the original pcb and solder it to a replacement ?

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