Data recovery from USB drives considers platter level and firm level failures as two of the key criteria. USB devices consist of external disk drives, pen drives, data cards, external memory devices and sticks. The architecture of these devices varies in file systems, root sector, storage pattern, logical drive and volumes etc. most of them are used only for data storage while a few of them may be used as secondary booting devices in case of primary disk failure. Nature of disk damages in USB drives varies from that of fixed drives with respect to hardware components, while the logical failure remains more or less the same.
USB based HDD: – USB electronic components are add-ons to the layer that comes between the disk drive and the computer to which they are connected. PCB in the external case of the drive acts as the powering medium, functional control channel and data integrity maintenance tool. Failure of this PCB can result in extended effects on the internal functionality of the drive in many ways. Inaccessibility of the drive, corrupt file-system, bad sector origin & growth, read write head damages, platter scratches, spindle breakdown and other mechanical problems can occur within the drive when the PCB gets short circuited.
PCB Scan: – Scanning process starts at the PCB level when the drive becomes inaccessible. Firmware stored in the PCB ROM can get corrupt due to short circuit. In such cases, the initial diagnosis of PCB will reveal the damages explicitly. So the firmware data has to be replaced before proceeding with testing of other parts. Only then the scanner will be able to detect other types of failures as the Rom acts as communication medium between the PCB assembly and external devices & controls.
Firmware ROM repair: – Serial ATA compatible recovery tools will be able to identify the exact nature of corrupt firmware data stored within the PCB ROM. This error can be fixed with the help of another donor PCB ROM which has the same type of firmware in the failed ROM. The technician connects both the ROM components with the help of firmware fixing tool. It erases the corrupt firmware data in the failed ROM and replaces it by transferring the data from Donor ROM. Once this process is complete, the failed PCB is ready for further scanning process.
Detecting PHY error status: – The PCB of the USB hard drive displays the following error messages, depending on the nature of failure. These errors are called PHY states.
PHY-State Zero indicates problems within the circuit design like burnt out fuse, power-converter-chip damages and other chip level components on board. In such cases the OS in the main computer will display an error message related to undetected device. Now the technician will try to zero in on the exact error by individual component testing with the help of PCB diagnostic tool. Once the errors are found, he will try to replace defective chips with active chips from another donor PCB. He takes care of choosing the donor board which is completely compatible with the defective board. For example Serial ATA compatible boards from Seagate needs the same type of donor boards from the same company. This process may take several hours as the removal and replacement of chip level components calls for de-soldering and re-soldering or disassembly and reassembly of pins by the tool.
PHY-State One is an indication of loose pin assembly with the PCB. It could also be due to lose Serial ATA connector and wiring on the board. In such cases the device gets detected by the computer but no connectivity can be established. The PCB repair tool is used to replace the non functional SATA connectors and cables on board.
PHY-State three is an indication of failed micro-controller unit on the PCB. The only option is to replace the unit with a functional one from compatible donor board.
Once the problems with the PCB are set right, the USB HDD is ready for further hardware component scan. Further scanning is done on Actuator arm and read-write head, disk spindle, platter and other micro components connected to the drive. Some of the common hardware problems with these devices could be one among the following.
Heated platter: – The disk platters rotate at a standard speed of 7,200RPM while the read write head in the actuator arm performs the disk/IO operations from a distance of 5 to 10 microns from the platters. Electromagnetic field between the two components makes this process of read and write possible. The hard disk platters have high degree of tolerance for withstanding the consistent stress on them. Mechanical faults due to physical damages, deposition of dust on the platters and other stresses on the spindle platter assembly can create friction in the movement of palters. Such friction can create enormous amount of heat due to the rotation speed of the platters. It can lead to bad sectors formation and physical damages to tracks and sectors within each platter. In some cases the “spacer plastic film” between the platters can melt, causing permanent damages to the platter surface.
When such a status is detected, the drive should be immediately opened and platter assembly needs to be fine tuned. This can be done with the help of spindle assembly repair toolkit which consists of spindle tool, motor repair tool and spindle replacement tool. The technician will use the combination of all these tools to set the spindle’s vertical position back to its original stance, free the stuck motor and read-write head. In the next step he checks the platters for any physical damages. In case of any critical damages they are replaced with the help of platter exchange tool and data is mirrored into the donor platter.
Now the donor platters are fitted into the USB drive assembly and the drive is scanned for logical errors. Once these bugs are fixed, the drive is ready for use as most of the data is recovered by this time.