Technical activities like data management, data warehousing, and even data recovery techniques have become indispensable in every business sector - may it be IT or others. However, in spite of the data technology advancement the technical hazards can't be ignored. Data loss is a common phenomena that can occur anytime either from physical or logical (software, programming etc) damages to the storage media. For this, Data Recovery, a procedure to salvage lost, damaged or inaccessible data from the secondary storage media has become necessary. Though a number of data recovery software are available in the market to deal with the problem, but basic procedures to recover lost data remain the same. Data can be recovered from storage media like CDs, DVDs, USB flash, solid state drives (SSD), REID, or external or internal Hard Disk drives.
When to conduct Data Recovery?
The process of Data Recovery depends on the cause of the data loss. There are three major conditions when data recovery becomes necessary.
1. Operating System failure: In case of a Operating System failure - especially in case of a single disk, single partition or single OS system - the primary aim is to copy all the necessary data to another disk with the help of a Live CD, which uses a file manager or a software to transfer the data from the system disk to the back-up drives. This can be done by disk partitioning and consequently copying the necessary data from the corrupted OS system files to another partition.
2. Disk-level failure: This situation involves failures related to the file system, hard disk, or disk partitioning. Here the solution to recover data depends on the type of disk failure that has occurred. In all these situations the data is not easily readable and hence repairing the partition table or the file system or the boot record becomes essential. From software-based techniques for recovering corrupted files to hardware replacement, any hardware-recovery technique can be undertaken here.
3. Files Deleted: Files can get deleted anytime, either because of unscheduled shut down or by mistake or because of any other technical fault. However, the files are not actually permanently deleted even after they are deleted from the Recycle Bin. It's only their reference structure in the directory that is deleted to create space for other files. Such files can be also recovered. This process can be used in case of forensic applications or espionage.
Techniques of Data Recovery
a. Physical Data Recovery: Situations often arise when the hard disk is not accessible by the Window's Disk management or BIOS or other hard disk utilities. Under such circumstances, Physical data recovery becomes necessary because it is understandable that there is a physical damage in the hard disk drive. This type of Data Recovery process that requires recovering or salvaging files from crashed or damaged hard disk is known as Physical Data Recovery. Physical damage to the hard disk drive can occur due to various reasons such as humidity variations, extreme temperature, shock or force, exposure to moisture, spike or surge in power, or if mechanical and electronic components in the disk are defective. Likewise, depending on the reason for the damage, data recovery procedures also differ. Some of the Physical data recovery procedures are: Replacing the damaged Printed Circuit Board (PCB) with a similar PCB from a usable drive, replacing the damaged read/write head assembly with corresponding parts from a usable drive, and removal of disk from the damaged hard disk and installing it in a usable drive.
b. Logical Data Recovery: Unlike in case of Physical data recovery where a hard disk repair has to be made, Logical data recovery is undertaken if the hard drive is perfectly working but the BIOS, though recognizes the hard drive, reports an error in data reading. In Logical recovery, the files that are corrupted by user error or virus are rebuilt. For instance, typical cases like overwritten data, which are often assumed to be permanently unrecoverable, can be recovered. However, though the process is not yet full proof but the renowned Guttman Method is being used by various disk scrubbing software packages to recover data. Other than this, 'Corrupt File System' where the data in the hard drive is unreadable due to some file system error or damage, can also be recovered by expert end users. Finally, Online data recovery is another process that comes under Logical data recovery. Though the process is the same as any software-based recovery, but here the recovery is performed over the Internet without availability of any drive.
c. MFM (Magnetic Force Microscopy): Magnetic Force Microscopy is the most latest technology that is used to detect and recover lost data. Through the concept of magnetic field, the MFM scans magnetic sample. Through this scan the magnetic structure of the hard disk surface is reconstructed to enable data access. Typically, this type of scanning method by the MFM is called the "lift height" method.
d. Fragmentation: Though fragmentation is not an efficient method to track lost files if the file size is too large, but it is a good option if the target file is small in size. Here the aim is to rebuild files, which are inaccessible because of accidental deletion, without using FAT entry.
When to conduct Data Recovery?
The process of Data Recovery depends on the cause of the data loss. There are three major conditions when data recovery becomes necessary.
1. Operating System failure: In case of a Operating System failure - especially in case of a single disk, single partition or single OS system - the primary aim is to copy all the necessary data to another disk with the help of a Live CD, which uses a file manager or a software to transfer the data from the system disk to the back-up drives. This can be done by disk partitioning and consequently copying the necessary data from the corrupted OS system files to another partition.
2. Disk-level failure: This situation involves failures related to the file system, hard disk, or disk partitioning. Here the solution to recover data depends on the type of disk failure that has occurred. In all these situations the data is not easily readable and hence repairing the partition table or the file system or the boot record becomes essential. From software-based techniques for recovering corrupted files to hardware replacement, any hardware-recovery technique can be undertaken here.
3. Files Deleted: Files can get deleted anytime, either because of unscheduled shut down or by mistake or because of any other technical fault. However, the files are not actually permanently deleted even after they are deleted from the Recycle Bin. It's only their reference structure in the directory that is deleted to create space for other files. Such files can be also recovered. This process can be used in case of forensic applications or espionage.
Techniques of Data Recovery
a. Physical Data Recovery: Situations often arise when the hard disk is not accessible by the Window's Disk management or BIOS or other hard disk utilities. Under such circumstances, Physical data recovery becomes necessary because it is understandable that there is a physical damage in the hard disk drive. This type of Data Recovery process that requires recovering or salvaging files from crashed or damaged hard disk is known as Physical Data Recovery. Physical damage to the hard disk drive can occur due to various reasons such as humidity variations, extreme temperature, shock or force, exposure to moisture, spike or surge in power, or if mechanical and electronic components in the disk are defective. Likewise, depending on the reason for the damage, data recovery procedures also differ. Some of the Physical data recovery procedures are: Replacing the damaged Printed Circuit Board (PCB) with a similar PCB from a usable drive, replacing the damaged read/write head assembly with corresponding parts from a usable drive, and removal of disk from the damaged hard disk and installing it in a usable drive.
b. Logical Data Recovery: Unlike in case of Physical data recovery where a hard disk repair has to be made, Logical data recovery is undertaken if the hard drive is perfectly working but the BIOS, though recognizes the hard drive, reports an error in data reading. In Logical recovery, the files that are corrupted by user error or virus are rebuilt. For instance, typical cases like overwritten data, which are often assumed to be permanently unrecoverable, can be recovered. However, though the process is not yet full proof but the renowned Guttman Method is being used by various disk scrubbing software packages to recover data. Other than this, 'Corrupt File System' where the data in the hard drive is unreadable due to some file system error or damage, can also be recovered by expert end users. Finally, Online data recovery is another process that comes under Logical data recovery. Though the process is the same as any software-based recovery, but here the recovery is performed over the Internet without availability of any drive.
c. MFM (Magnetic Force Microscopy): Magnetic Force Microscopy is the most latest technology that is used to detect and recover lost data. Through the concept of magnetic field, the MFM scans magnetic sample. Through this scan the magnetic structure of the hard disk surface is reconstructed to enable data access. Typically, this type of scanning method by the MFM is called the "lift height" method.
d. Fragmentation: Though fragmentation is not an efficient method to track lost files if the file size is too large, but it is a good option if the target file is small in size. Here the aim is to rebuild files, which are inaccessible because of accidental deletion, without using FAT entry.
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