Data Recovery Services

Part of the ACE Data Group, LLC, Data Recovery Services has extended its capabilities to a full range of Solid State Drive (SSD) devices based on the NAND flash memory technology. Offered services cover full range of SSDs for all makes and models and include both logical (file system damage, deleted data, and reformatted media) and hardware (physical damage or operating failure) data recovery.

Solid State Drives has become a ‘must have’ feature in high end laptops, netbooks and tablets. However, they represent a fairly new technology in the storage market. Flash drives (like USB thumb drives, memory cards in camcorders and cameras) have been used for years, but this technology has grown to the point where it rivals the traditional hard disk drives (HDDs) using the same form factor. At first glance, there are a few advantages to solid state drives compared to traditional hard disk drives: no moving parts, less power consumption, faster access times and silent operation. It is no wonder that the manufacturers’ marketing departments have been drawing the public’s attention to these advantages.

Most SSDs use advanced controller technologies to improve the reliability and speed. The architecture inside a high performance SSD is more complicated than that in most RAID systems. Individual non-volatile NAND flash memory chips that form an SSD are relatively slow. The performance is scaled when the number of them is used in parallel inside an SSD. It allows increasing the bandwidth and effectively hiding the high latencies of the individual NAND flash chips. To make the drives even faster, such techniques as data striping (like in RAIDs) and interleaving are implemented.

Flash memory stores data in individual memory cells. There are two types of NAND flash memory – single-level cell (SLC) which stores 1 bit of data per cell and multi-level cell (MLC) currently capable of storing 2 bits per cell. The MLC memory is cheaper since it has more density, but it also results in the possibility of more errors and less write/erase cycles. Errors that appear during normal device operation can be detected and corrected by the controller using error correction code (ECC). NAND memory is accessed by blocks. Blocks available to high level software on a logical level are mapped to physical blocks by the controller. Any block needs to be erased before it can be written to. As a result, the device’s durability is measured in write/erase cycles. To ensure that no single block prematurely fails due to a high number of write/erase cycles, SSDs employ a technique called ‘wear leveling’. Wear leveling dynamically maps logical blocks to physical blocks in such a way as to ensure that write/erase cycles are evenly distributed across all available blocks. When any block wears out to the point it cannot reliably store data anymore, the controller either remaps such block to a spare one from an available excess capacity pool or just mark it as bad. Such technique is called bad block management.

The management algorithms and techniques such as advanced error correcting, wear leveling, and bad block management maximize the drive’s operating life and extends system-level endurance, but complicate the design. The algorithms which map logical addresses to physical media locations vary from manufacturer to manufacturer, and the details are closely guarded commercial secrets. All these technologies used in SSDs to extend the reliability at the same time complicate the data recovery process immensely in the case of a failure.

“Our team has developed an advanced solid storage drive recovery process of rebuilding multiple sets of NAND flash memory dumps. The process consists of reading individual NAND flash memory chips into raw images, then applying reverse-engineered ECC and special mapping algorithms to unscramble each image and assembling the numerous unscrambled sets into a single full drive image. The resulting image then can be processed using normal data recovery methods,” said Yevgeniy Tolkunov, director of R&D, Data Recovery Services.