We always talk about data recovery tools, data recovery services but seldom do we know about the techniques used with the tools and services. The following are some most common data recovery technologies and some creative data recovery technologies. Let’s have a review together.
* Logical data recovery
In a data loss situation when the hard drive is perfectly fine and the BIOS recognizes the hard drive but reports a read error, logical data recovery technique is very helpful. Here the files that are damaged or corrupted by any user error or virus attack are rebuilt rather than repairing the hard drive.
The first, consistency checking, involves scanning the logical structure of the disk and checking to make sure that it is consistent with its specification. For instance, in most file systems, a directory must have at least two entries: a dot (.) entry that points to itself, and a dot-dot (..) entry that points to its parent. A file system repair program can read each directory and make sure that these entries exist and point to the correct directories. If they do not, an error message can be printed and the problem corrected. Both chkdsk and fsck work in this fashion. This strategy suffers from two major problems. First, if the file system is sufficiently damaged, the consistency check can fail completely. In this case, the repair program may crash trying to deal with the mangled input, or it may not recognize the drive as having a valid file system at all. The second issue that arises is the disregard for data files. If chkdsk finds a data file to be out of place or unexplainable, it may delete the file without asking. This is done so that the operating system may run smoother, but the files deleted are often important user files which cannot be replaced. Similar issues arise when using system restore disks (often provided with proprietary systems like Dell and Compaq), which restore the operating system by removing the previous installation. This problem can often be avoided by installing the operating system on a separate partition from your user data.
Data Carving is a data recovery technique that allows for data with no file system allocation information to be extracted by identifying sectors and clusters belonging to the file. Data Carving usually searches through raw sectors looking for specific desired file signatures. The fact that there is no allocation information means that the investigator must specify a block size of data to carve out upon finding a matching file signature, or the carving software must infer it from other information on the media. There is a requirement that the beginning of the file still be present and that there is (depending on how common the file signature is) a risk of many false hits. Data carving, also known as file carving, has traditionally required that the files recovered be located in sequential sectors (rather than fragmented) as there is no allocation information to point to fragmented file portions. Recent developments in file carving algorithms have led to tools that can recover files that are fragmented into multiple pieces. Carving tends is a time and resource intensive operation.
When the FAT entry is lost during accidental file deletion, formatting or partition deletion that particular block of hard drive becomes inaccessible. Some data recovery software makes an attempt to rebuild the files without a FAT entry. This technique is very efficient if the file size is smaller than the clusters size. But it is inefficient in recovery the larger files.
* MFM (Magnetic Force Microscopy)
MFM is the latest technique that uses a sharp tip attached to a flexible cantilever placed close to the surface of the damaged device where it interacts with the stray magnetic field. While the tip is moving across the magnetic device, it is evaluated to detect the lost data. The technique turns out each track that contains an image of everything ever written to it, and finally recovers the lost data.
* Firmware Service Area Emulation Technology
The Hard Drive Firmware Service Area Emulation Technology is a new technology which is used to initialize the firmware information of a specific hard drive by loading predefined SA resource file onto the memory of the external emulator. In another word, the hard drive will boot itself from the information on the emulator rather than from the native firmware information. By using the SA emulator, user can access the data area directly without repairing the corrupted firmware. This technology is quite similar to the Hot Swap operation where the emulation of SA is achieved by a donor hard drive. Because of the nature of the adaptive information, many modern hard drives are not facilitated themselves to achieve a successful Hot Swap operation. But, by using an external SA emulator, this problem can be resolved. This new technology is so far used in one tool called Data Compass to handle Hitachi disks’ firmware failure. Data Compass can bypass the firmware failure and access to the data area and recover the wanted data easily.
Download the datasheet of this technology here
* Shadow Disk Technology
Shadow Disk Technology is one innovative technology for disaster data recovery. ShadowDisk technology, a very different technology from traditional image technologies. By this technique, there is no need to create an image separately during the whole data recovery process. Instead, an index log will be created synchronously to record the sectors retrieved from a source disk on the counterpoint section of a ShadowDisk. Any repetitive read attempts onto the retrieved sectors will be turned to the ShadowDisk directly according to the index log. Thus, it can reduce read times on the source disk to preserve its original and intact situation. Furthermore, ShadowDisk technique can read any specific location of a source disk according to the value of the LBA, which traditional image technique is far to reach. This technology is so far used with Data Compass too.
Download the datasheet of this technology here
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