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What is Data Recovery? what are the methods and techniques of data recovery. How to restore data.
Data recovery, restoration data, restore data, resave data, or data retrieval - procedure of extraction information from the storage device or the data medium in a case when it can't be read by a normal method. Or isn't defined or recognized by an operating system or the data reading device. Restoration can be done from any computer carrier, including CD, the DVD, hard drives, a flash memory, video recorders, media players, mobile phones, smart phones etc. As a rule usually the data having or representing a certain value are subject to restoration.
The reasons of loss data on storage carriers
Need for restoration data can arise when the data medium has the hardware, program or mechanical damages, or when data files were only marked as deleted, file structures are partially re-recorded, but files still continue to be stored before will be re-recorded or overwritten completely.
Some common causes for need of restoration of data are given in below:
Floppy drive, FDD diskette: usually it ceases to be read owing to hardware-software errors in case of data record, or in case of accidental deleting or cleaning as formatting. In case of physical damages scratches and surface pollution.
Compact disk: Owing to hardware-software errors in case of data record, fast accidental cleaning of a re-recorded disk, damage/distortion of the transparent, registered or reflecting layer, a crack in plastics and scratches on a surface.
Flash memory on the basis of NAND, USB or SD flash memory card: Owing to the wrong extraction of the device from computer, unauthorized formatting, accidental deleting. Breakage of the printed circuit board (PCB), corrupting of contacts or connection chips, combustion of power supply regulators, damage of controllers, static electricity, cracks in the printed circuit board. Water dampness and excessive heating, degradation of storage cells of NAND bringing to multiple errors, low-quality assembly at plant the manufacturer bringing to bad contact legs and bad soldering of radio electronic components.
Hard drive: Unauthorized formatting, accidental deleting, damage of sectors containing the control firmware, damage of area of boot strap loading, not readability of sectors responsible for placement of directories and folders on a disk drive. Failure in the ROM and CPU controller, scratch on surfaces hard disks drive, crash or magnetic head, damage the unit of magnetic heads, burnout of the preamp switching of heads, defects surfaces of a magnetic plate, the partial degaussing, aging of a magneto-resistive (MRI) head element, degradation and change of parameters of reading heads, distortion thermo - calibrations or loss information on precision parameters of reading zones and drive surfaces.
Restoration methods :
Now there are three main methods of restoration of data. The method is selected depending on the arisen failure of the drive.
1 . The program method is used in case of completely operational and good hard disk drive and represents sector by sector logical scan and read with data extraction.
2. Hardware-software method apply when the program method won't yield result.
3 . The physical method: slower also is applied when plates have scratches, surface abrasions, and damages or there are offsets of a packet of plates and there is no opportunity to read data having repaired a hard drive. In this case the method of direct reading from plates of a hard drive is used.
2. The hardware-software method
Hardware-software method is required in case of physical damage of the drive. Here it is necessary to focus attention on drive type: whether flexible it is a magnetic disk (FLOPPY DRIVE, FDD), a hard magnetic disk (HDD drive), flash (drive NAND-Flash, monolithic) or CD/DVD/BD. Let's consider the main types of carriers and their failure. The drive on a floppy disk (FDD) the main failure is so-called degaussing. Meets most often when passing magnetic detectors in shops, subway, airports. It is possible to recover data only from not degaussed areas of the drive. As the failure connected to physical damage of the carrier, such as the scratches, the gross contamination meets. Each case needs to be considered individually and only after that to predict result of data restoration .
The drives CD/DVD/BR Optical drives can have the different reasons of impossibility of data reading:
1 . Mechanical damage of the transparent layer or damage reflecting layer
2. Chemical expansion, decay, of the transparent layer or expansion of a registered layer (at writeable disks) corrosion of a reflecting layer
3. Violation of a data structure owing to hardware-software errors in case of data record owing to the
wrong data the most frequent reasons of not readability of disks are damage of a reflecting and transparent layer, and also expansion of a registered layer at writeable disks. In case of formation of scratches on a disk surface, it is possible to apply polishing of a working surface that will lead to deleting unwanted damages and will improve data reading, however in case of formation of cracks, dangerously to use this method as in case of the subsequent reading the disk can fail in the disk drive under the influence of centrifugal force. Damage of a mirror foil layer covering of a disk (aging of metal, scratch) most of all complicates restoration of data.
NAND-Flash, SSD drive, monolithic flash, solid state and monocrystal flash. It is portable carry USB Flash, SSD disks to this type of drives, the memory sticks SD, miniSD, microSD, xD, MS, M2, Compact Flash.
The most widespread technical failure: Logical failure the Drive has no visible physical damages and is identified in system. The problem arises in case of access attempt or record/data reading. There is this failure in the most different cases. One of the most common causes ? the wrong extraction of the device from the computer. In case of logical failure possibly to recover data by means of programs for restoration of data. Damages of a program code or chip of data storage flash. The reason of damage of a program code or the so-called translator responsible for internal data transformation and storage layout on a chip of flash memory. Due to the big packing density of the modern chips of memory quality of storage cells worsens it carries to loosening of storage of the logic levels in a memory chip a flash. In the modern chips of memory ECC correction correcting bit or point errors is used. And when the quantity of errors on a chip a flash increases to such an extent that them it is impossible to correct or correct flash memory more isn't read correctly and stops the operation. Mechanical damages the disk stopped incorrect operation as a result of any physical impact (falling, hit of moisture, a bend, compression etc.) . Cause of defect, most often, in breakage of a board or corrupting of contacts and components. It is possible to recover data if to correct breakage: to replace a faulty component or to recover the broken contact. It is also possible to consider the memories this directly from the chip, using the special equipment. Electrical damages the Reason of electrical damages consists in static shock or in a problem with a supply. As a result power supply regulators, diodes, controllers can burn down, sometimes there is also a burning-off of the memory flash. Restoration of data is made as well as in the previous case: changeover of components or reading from memory chips directly if it is possible.
The drive on a hard magnetic disk (Hard drive, HDD) Today these drives are considered the most capacious and rather fast, but very vulnerable to electrical and mechanical influences. In case of a supply overvoltage, or unstable tension there can be a thermal breakdown of a board of the controller, and also switch preamplifier breakthrough inside hermetic chamber. In the first case the board of the controller of a hard drive fails and procedure of restoration of data comes to an end on its changeover with transfer of the adaptive parameters of the faulty drive on a new board. However cases when as a result of breakthrough the electronics hermetic chamber fail meet, in this case changeover of MHA (magnetic head assembly) is necessary that inherently is labor-consuming and expensive procedure. In case of mechanical damages, such as falling, shock, deformation, interference of the expert in a hermetic chamber is necessary as for clearing up of possibility of restoration of data, it is necessary to analyze a status of magnetic disks. In case of origin of concentric, radial scratches or grazes by surfaces of plates, probability of restoration of data decreases as ideally smooth and equal surface of magnetic disks is necessary for successful data reading. Also there are problems with jamming brushless spindle motor. In this case experts resort to transplantation of all packet of magnetic disks on operational spindle motor, or bearing changeover without extraction of a packet of a hard drive then its calibration and the magnetic head assembly setup is carried out.
3. Deep physical read method
In case of serious damages of a surface of a hard drive remove a whole assembled plate packet and separate plates by one separately. Then them wash out and make process prepare scratches and dents for achievement of a smooth surface. If in a packet of a disk of a plate them read each one by one on the special equipment under slower rotational speed without allowing hit of heads in a zone of scratch and thus setting up parameters of reading heads. Then the read sector images from each surface combine together and obtain a full hard drive image. It is possible transfer to a normal hard drive which can be read already with a regular normal method. Rather often the failure connected to corrupting of the so-called control footing (start booting) of the drive meets. Some parts (not all) of the start boot control can be taken from similar drives and are written in faulty by means of the special equipment with which, as a rule, locate the service centers which are engaged in restoration of data at the professional grade. In that case it is necessary to recover the lost parts resorting to the logical analysis of tests which were launched at plant the manufacturer or to replace the microcode completely on more suitable. As practice shows, attempts of unskilled interference in structure of the master boot control code of the drive, firmware, ROM, to regret, involve final and irrevocable loss of data.
How to select the engineer and best data recovery service which will provide you the guaranteed restoration of data read in the following article.....
A full description of the methods in data recovery
1 . Program or software method of restoration of data.
The program or software method - restoration of data without disassembling of physical interference in the drive device, and also in functioning of the micro program and structure of modules of the control footing. This method is applied in cases when operability of the drive is saved, but for any of several reasons the no data access, being stored on it, is lost. Formatting of logical disks, unsuccessful change of logical geometry of the drive, deleting data information, the partial or final fracture of file system, as information on structure of placement of data on the drive can become the reason of it. Often in the listed cases it is possible to recover the most part of data, however cases when restoration of the lost data is impossible (a special case meet it is possible to consider copying of data). For automation of process of restoration the set of programs, including free is written. Structure restoration in case of formatting of a logical disk or the section, the structure and attributes of data aren't broken, but changes or reversed (it is brought into start state) information on layout of data on this drive. In case of the quick format the small part of the file table is updated, the part of the official records remains, it is necessary to interpret only it and to read data in the necessary order. Full formatting can update all file table, therefore restoration of a file structure and folders not always possibly. For restoration of data without information on structure it is possible to use restoration of files on signatures. If there was a damage of file system as a result of program failure or failure of the carrier, programs for restoration of data can recover the part of information depending on volume of damages. Restoration data of file system when deleting data, actually, data physically remain on the drive, however in file system more aren't displayed, and a place on the carrier where they settle down, is marked as the free and ready to record of new information. In this case attributes of files change. In case of record in this section or a logical disk there can be the partial or full substitution of the data marked, as remote. Similar files can be read and recovered easily with all attributes and information on layout, having read the official records of file system. There are as the program only for restoration of removed data, and end-to-end solutions, where restoration of remove data ? only one of functions. Also there are special programs ? intended for destruction of data. After the correct use of such programs restoration data is impossible. Restoration on signatures in a case when reconstruction of file system is impossible owing to any reasons, can still be recovered some files, using restoration on signatures. In case of this type of restoration there is a sector by sector scanning of the drive about existence of known signatures of files. The basic principle of operation of algorithms of signature search same, as at the very first antivirus. As the antivirus scans the file in search of sections of the data matching known fragments of a code of viruses, and the algorithms of signature search which are using in programs for restoration of data, read out information from a disk surface in hope to meet familiar sections of data. Titles of many types of files contain characteristic strings. For example, files contain JFIF string in the JPEG format, ZIP archives begin with PK characters, and the documents PDF begin with characters %PDF. Some files (for example, text and HTML files) don't possess characteristic signatures, but can be determined by indirect signs since contain only characters from the table ASCII. The file Begins with: avi - 5249 bmp - 424D tif - 4949 doc - D0CF docx - 504B jpeg - FFD8 png - 8950 signature by results of scanning the file list, sorted by type is issued, most often. Information on layout of files isn't recovered. It is good to apply this type of restoration to restoration of photos from memory sticks as data on a card same and register, generally, strictly sequentially, without fragmentation. The Majority of programs some methods of restoration for one scanning allow to apply the mixed restoration at the same time. As a result the greatest possible result is given when using this program.