DATA RECOVERY – USB/FLASH Memory Recovery
Unlike conventional hard drives where data is stored magnetically, portable flash memory uses solid state (i.e.microchip-based) memory based on a format called NAND memory.
Flash memory is often seen as a more reliable means of storage due to lack of mechanical parts. However, there are other factors relating to the design and manufacture of flash memory devices that present opportunities for failure and data loss. The key characteristic of NAND memory is that it ‘wears out’ after approximately 100,000 write cycles. For this reason, flash memory devices use a controller chip to dynamically manage the storage of data so that all storage blocks get written to once before any given block incurs a second data write event, and so on in such a way as to extend the life of the memory. A 3MB digital photo will typically occupy 1500 non-contiguous blocks of flash memory. Add in some re-arrangement of these 1500 blocks which will happen each time you view the photo from the device, and you can begin to get a feel for the level of organisation (and potential disorganisation) of the underlying data in a raw sequential dump (i.e a snapshot) of data from a flash microchip.
Another characteristic of this memory type is that the data is written to (and deleted from) the device by the application of carefully-timed tiny voltage signals. The flip-side of this is that the devices themselves are highly voltage sensitive, and that minor unexpected fluctuations in voltage at an inopportune moment can corrupt data beyond recovery.
The simplest form of failure is caused by physical damage to the device, and this can be caused by accidentally hitting the device while it is protruding from a USB port on your computer, or possibly by straining the connector if left in your pocket, for instance. These types of failures can usually be resolved by re-making the connections between the USB connector and the printed circuit board. If the silver-coloured USB connector on your memory key feels loose, then chances are that this is the underlying issue. Our success rate in such cases is virtually 100%.
Internal Electronic Failure
The more common failure involves failure of an internal component, such as the oscillator or controller chip. It is usually impossible to source exact parts to replace these, and so the remedy involves de-soldering the actual memory microchip(s) from the circuit, obtaining a raw dump of the data from the microchip(s), and then translating the dump to obtain the original data structure and files.
The raw data dump could be thought of as all of the pages on an encyclopaedia torn out and laid randomly on the floor with page numbers deleted. The challenge is to re-order the pages correctly so that the information makes sense. For every 1MB of flash memory, there are usually approx 250,000 ‘pages’ of data to re-order.
Since there are so many thousands of variations of devices in the market, and so many combinations of controller and memory chips, each new job is usually different than the last.