Hard Drive Recovery: Logical and Physical

Hard drive recovery is the process of extracting data with the help of software utilities or disk internals level operations plus software tools from logically or physically corrupted hard drive. The best practice is to create a disk image before carrying out any recovery. A disk image is an exact copy of a hard drive or an affected partition/volume. It is created to avoid any data loss during the recovery procedure. We should always maintain an updated data backup on a secondary storage device like an external hard drive to avoid any recovery requirements. If we have all the data backed up, we can simply perform a clean reinstall and restore the data as per our last directory structure. In addition to this we should use hard drives with highest MTBF (Mean Time Between Failure) rating and S.M.A.R.T (Self-Monitoring, Analysis and Reporting Technology) support. We need to enable the S.M.A.R.T option in system BIOS (Basic Input Output System) to make it check the hard drive for any physical issues and proactively inform us.

A hard drive is divided into various sub-parts. They can be broadly divided as moving and non-moving components. The moving components are: Spindle Motor and Spindle, Read/Write Head, Actuator Arm, Head Actuator and Platters. The non-moving components are: 1.) Hard Disk Controller 2.) Head/Disk Assembly 3.) PCB (Printed Circuit Board) 4.) Input/Output Connector etc.

The Hard drive Recovery can be done by following these two approaches as per logical or physical drive failure:

i.) Hard Drive Recovery Software: These are utilities that are developed based on file system structure information to enable the software to find the files, file signature information to recognize the file header and footer and advanced scanning algorithms to efficiently scan the hard drive. A home user can easily use these software to scan his hard drive after data loss. Some data recovery software also offer bootable media like CD or DVD to boot the system from them in case the system is not able to boot. We need to attach an external hard drive (USB/Firewire: IEEE 1394) or flash drive (USB). We can boot the system using the bootable media and scan the hard drive. We can even preview the lost files in good quality data recovery software and then save the files in the external hard drive or flash drive.

ii.) Hard Drive Recovery Service:  The Hard Drive Recovery service for of lost data is carried out by Data Recovery experts with rich industrial experience and exposure to the hard disk internals. Such recovery procedures often deal with dismantling the hard drive and repairing or even replacing certain components like the read/write head, actuator arm if they have failed. The Hard Drive Recovery is performed under sterilized environment of Clean rooms. The lab environment of Clean rooms offer controlled temperature, pressure, humidity and no dust particles to ensure maximum protection to hard disk internals.

The data that we save in the hard drive actually gets stored on the platters. The less these platters are the easier it is to recover the lost data. In case, a platter has physically failed has developed physical bad sectors we cannot retrieve our lost data from that platter and the area affected by physical bad sectors will become unavailable for recovery due to unreadable media. Such physical bad sectors cannot be repaired or removed like the logical bad sectors.

Hard drives offer large storage capacity and are very cost effective as compared to other storage media. Today hard drives are available in the market up to 2 TB of storage. When we delete data in any operating system like Microsoft Windows, Apple Mac OS or Linux, the files don't get deleted in actual. It is just the file reference that gets removed by the operating system. In other words, the files still remain on the hard drive though we cannot access them using the operating system. The same is true in case of lost or corrupted data but the corrupted data files need to be repaired as well.

The partition or volume loss also follows the same rule that is the data still resides in the partitions or volumes but we cannot access them. The common reasons behind such errors are system software conflicts, erroneous deletion, operating system warning related to partition health, virus infection etc. If we face any of the above issues and the hard drive data becomes inaccessible, we should not use the hard drive any further other than Data Recovery from it in order to avoid any disk overwriting. After the lost files get replaced by any erroneous user operations like overwriting the drive with some new files like by a paste operation, it becomes impossible to recover the files as their start and end points get changed by the new files.