Hard Disk Data Recovery
Data Recovery works almost 90% But some hard disk are the exceptional case, where hard disk is not readable or rewritable, Fortunately, the information that still remains on the storage can be recovered to a safe location. Recovery chances depend much on the data loss situation itself, but you should take into account that no information is recoverable after overwriting. For this reason you should never write anything to the storage until the last file is recovered.
Data recovery software serve to get data back after information loss with maximum possible result. Commonly, data recovery operation bases on storage scan to find specific information (deleted files, lost file systems) and assemble structures of a damaged file system.
Hard Disk Data recovery chances
Data recovery chances depend much on the actual cause of data loss and further user’s actions. To get maximum data recovery result it’s strongly recommended to stop any write access to the storage and run data recovery software immediately.
Data loss caused by file deletion
Any deleted file remains on the storage until the storage space is re-used by other data. After file deletion OS may re-use disk space anytime to store a new file. Thus, even minor write to the storage may cause permanent data loss. Internet browser may result in overwriting of deleted files as well by saving cache or cookies to the storage. If you install the software to the same drive, your data are also under the risk of overwriting. Another factor that influences data recovery chances after file deletion is file deletion algorithm dependent on the file system. For Windows NTFS file system recovery chances are quite high, because if file descriptor remains on the disk, the software may easily take all required information about the file. Unlike NTFS, BSD UFS file system destroys information about file start, location and size permanently and together with high degree of file fragmentation typical of this file system leaves very slim chances for successful data recover. Other file systems (like FAT) feature average chances for data recovery. Here only part of information is destroyed (like information about file fragments), but information about file name, start and size still remains on disk. Heuristic algorithms still allow to ‘guess’ file fragments and recover good files. Please keep in mind, that due to lack of real information about allocation of file fragments any data recovery software may fail to detect real file position, especially if several fragmented files were deleted close to the same location on the storage. The scope of these factors make any file recovery software use a set of deterministic and heuristic algorithms to guess deleted file location. Please consider that these algorithms differ from vendor to vendor making recovery results differ as well.
Recovery after file system format
After file system format a part of information on the storage is destroyed due to overwriting with new information of a new file system. Again, data recovery chances after format depend much on the original and new file systems. For instance, if a file system was formatted with FAT, it overwrite huge amount of storage space at disk start with zeros (empty block allocation tables) and therefore destroys any previous data. Even if previous file system was also FAT, the information about allocation of previous files will be lost completely. Other file systems usually allocate more or fewer structures to different storage locations. Recovery chances are much dependent on original and new file systems. Sometimes recovery chances are higher if the file system is formatted with the same file system type (e.g. NTFS), sometimes – not (e.g. FAT over FAT has worse recovery chances than XFS over FAT).Efficient data recovery software usually produce quite good recovery result after file system format. Most file systems (except those like FAT) may still keep file allocation information, directory records, file names etc. that allows to successfully reconstruct the file system. However, since new structures are written to the disk, some user information can be damaged and some files or folders can be lost.
Recovery after file system damage
To this type of data loss data recovery software usually apply the same methods as for a formatted file system. Data recovery chances depend much on the actual file system damage that can be a damage of user files, file folders, file location, file name or all at once. Anyway, efficient data recovery software will help you achieve the highest possible data recovery results.
Loss of information about partition
This type of data loss cause is probably the most unsubstantial. Working with this type of damage data recovery software identifies file system start by known file system structures scanning the storage. If the loss didn’t affect the file system itself, the data can be retrieved in its original form in the full scope.
Note: Never try to recover data from a failed or failing storage yourself. You may cause permanent data loss. The only exception is RAID systems where storage redundancy allows to recover good data without a failed unit.
RAID failure may occur also effect file system. But if the file system remains intact, your RAID will have quite good data recovery chances ,the specifics article for more information about data recovery from RAID.
Recovery of wiped/overwritten data
It is simply impossible. The myth about the possibility to recover lost files after overwriting is inherent from successful attempts to recover data from old diskettes and hard disks. These devices (with storage capacity from kilobytes to megabytes) used very wide magnetic trace and simple digital encoding to store the information. For this reason it was possible to read ‘traces of data’ after wiping or overwriting by calibrating read ‘head’ sensitivity and position. Modern systems use very thin tracks, high precision of head calibration and extremely high signal frequency near to the top of technology limit. Performance of modern chips only allows to pick good discrete signal from disk platter and never identifies any ‘signal traces’. This scheme is impossible for any digital device (discrete signal frequency to handle such data lays much beyond the theoretical limit of electronic circuits).Please never trust those companies that claim to be able to recover data in this way.