Data Recovery Terminology

Actuator Arm

Refers to the entire assembly which positions the hard drive read/write heads over the platters and actuates back and forth over them. It is generally suspended between magnets at the rear end for balance and controlled by a servo winding. It also contains the ribbon which connects the heads and servo winding to the drive’s PCB. Generally in data recovery the entire assembly is replaced when a drive needs new heads as this is much easier to perform.

ATA

Advanced Technology Attachment. This is the standard protocol used to interface with the majority of hard drives and many other storage devices. The term doesn’t specifically refer to a particular cable or connection, but rather to the command set used in the back and forth communication of the computer to the device. However, the term is often used synonymously with PATA (Parallel ATA) which is the connection which uses ribbon cables commonly seen in older computers. SATA, or Serial ATA, also uses the ATA command set.

Bad Sector

A damaged or corrupted area on the hard disk platter where the drive is unable to read even after several attempts. A few bad sectors is expected within normal operation of a hard drive and can usually be handled by the drive through re-mapping the damaged area to another unused region of the physical platter. However having a large number of bad sectors will cause the computer operating system to hang or crash, or can even render the hard drive inoperable.

Blu-Ray

Refers to high density digital optical disks which can store 25 – 128GB of data. Typically they are used to store high definition video, however can also be used to store other computer data. The low cost of hard drives and flash media combined with the high cost of Blu-Ray media has made this an uncommon use for the disks.

CD or CD-ROM

Compact Disk. Refers to an optical disk used to store music tracks or digital data. Generally they are able to store about 700Mb of data. Music CD’s aren’t truly digital as the information is written in track form rather than sector form as in other data storage media.

CD-ROM Drive

Generally a term referring to devices that can read CD’s in a computer. Technically speaking, a CD-ROM drive can only read CD’s and not write data to them, a or CD Burner is needed for that (ROM = Read only Memory). However the term is commonly used to refer to all such devices.

Cluster

A cluster is the smallest chunk of data used by the operating system.  It may be a single sector size of 512 bytes or larger.  No matter how small an individual file is it will take up the size of at least one cluster.  When formatting a volume the cluster size can be user specified and should be selected based on intended file storage.  For systems with a lot of small files, a smaller cluster size is preferred as it will provide maximum storage.

Data Recovery

Data Recovery is a general term used to refer to the process of retrieving data that has been lost due to an accident or software/hardware malfunction. It may involve work to repair hardware, use of data recovery software, or even manual efforts to find and recover the desired data.  Some data backup & disaster recovery companies use the term interchangeably with disaster recovery which is the process or restoring data from a backup to it’s original system.

Encryption / Encrypted

A process by which data is scrambled using a cipher and key.  With most modern forms of encryption decrypting the data is impossible without the key (password).  Many devices including many WD USB hard drives and SSDs of various brands have a level of hardware encryption allowing the user to set a password even after data is written to the device.

Firmware

This refers to software which is contained within electronic hardware. In data recovery some people use this term referring to the service area of a hard drive.

Format or Formatted

Refers to the process of re-writing the filesystem of a hard drive or logical volume. A “quick format” only rewrites the file tables, and generally leaves most of the data in tact until it is later overwritten by other new data. Therefore, drives that have been quick formatted can usually have most data recovered. A “long format” on the other hand, actually zero’s out all sectors and cannot have it’s data recovered.

Partition

A partition, or logical volume, is a section of a hard drive that is divided off and usually contains it’s own filesystem. A single physical hard drive may have several partitions containing various filesystems. In a typical Windows system your operating system is located on a partition that is generally labeled “C:”, however you may have other partitions on the same drive such as a recovery partition to restore your computer to it’s factory settings. The layout of your partitions is specified in the partition table.

Partition Table

Referrs to a system stored on the hard drive or other media which contain the layout of the drive’s partitioning.  This is used to divide the physical disk into multiple logical volumes. The partition table also contains the information used to tell the computer which partition to boot from, what type of file system they each contain, etc.

Hard Drive (Hard Disk Drive, HDD)

A fixed disk arrangement generally 3.5″ wide in desktops and 2.5″ wide in laptops. They are the primary storage medium of most computer systems. Typical hard drives consist of a cylinder of spinning platters containing magnetically written data which is read / written using a fast moving armature with read/write heads attached at the tips.

IDE (Integrated Device Electronics)

Generally this term is used interchangeably with PATA.  The term was used referring to parallel ATA devices by IBM for many years while other manufacturers stuck with the more accurate & descriptive term Parallel ATA.

Initialize

This term as used in the Window operating system refers to the process of creating a partition table when none exists or none is recognized by the operating system.  In cases of hardware failure it’s common that Windows will begin prompting the user to “initialize” the disk.  If the option is selected a new partition table may be created over the existing one.

MBR (Master Boot Record)

This is a type of partition table common to most Windows machines and is found in the very first sector of the data on the drive.  It is limited to four partitions and a maximum size of 2TB per partition.  In newer systems it’s being replaced with the GPT partitioning structure.

Media Damage

When the platter surface of a HDD is physically damaged or degraded it may lead to bad sectors which cannot be read despite numerous attempts.  In severe cases this media damage may be catastrophic, destroying all sectors or the service area which is necessary to restore operation of the drive.

Monolithic (monolith)

In data recovery it refers to storage devices which are entirely built into a single chip. Many SD cards, MicroSD cards, thumb drives, and other flash media are produced this way. Rather than using a traditional PCB with the various components (such as the memory storage chip, power regulator, and control chip) surface mounted, they are all incorporated into a single chip. While this may cut down on the devices size and production cost, it makes data recovery extremely difficult and at times impossible. To recover data from such devices requires that the chip be stripped of it’s outer protective layer and have leads soldered into key parts of the internal circuitry. Only a few companies worldwide are able to handle these cases.

NV-RAM

Nonvolatile Random Access Memory. In Hitachi / IBM hard drives, this type of memory is used instead of ROM to store drive specific information on the PCB. However, it’s function is overall very similar. NV-RAM transfer is required for most models when replacing a damaged PCB.

PATA

Parallel ATA (Advanced Technology Attachment). Generally refers to the system of ribbon cables that attach from your motherboard to the hard drive and optical drives such as CD-ROM and DVD-ROM drives.

PCB

Printed Circuit Board. (Not to be confused with polychlorinated biphenyl). This refers to circuit boards that are actually assembled by printing metal, plastic, and other materials to form circuitry. They are often green, blue, or yellow in color, however may come in any color. On a hard drive it refers to the green or blue circuit board that is mounted externally on the housing. They are easily damaged by power surges and other causes of overvoltage. In fact some actually have circuitry built in that is designed to fail in the event of an overvoltage to protect other components. In years past computer technicians often could replace a PCB with another of the same model to recover data. However modern hard drive generally always require reprogramming as they contain drive specific parameters in the ROM or NV-RAM code.

RAID

Redundant Array of Inexpensive Disks. This refers to an arrangement where multiple disks are used to either store large amounts of data, increase throughput (speed), or both. RAID 0, which is not truly RAID as it isn’t redundant, is a simply system of striping data in fixed increments across multiple disks for increased speed. RAID 1 is a simple mirror system where all drives contain the same data. Other RAID configurations such as 5, 6, 10 use both striping and incorporate data redundancy. For more information about what RAID is and how it works please visit our RAID page.

RAM

Random Access Memory. This is a type of high speed temporary memory which is volatile in nature (erased every time it is powered off). Computers use this type of memory for currently running programs and files. Hard drives also have their own RAM which is built on the PCB and is used primarily as a pre-fetch buffer as well as to store the drives internal software.

Read/Write Heads

Small electromagnets and electromagnetic resistance sensors at the tip of the hard drive actuator arm. They are the devices that read/write magnetic data to and from the actual hard drive platter surface. They are extremely sensitive (required for their operation) and therefore are also damaged very easily. Hard drive read/write heads are one of the most common parts in a modern hard drive to fail. Replacement requires work in a data recovery clean room and is therefore often very expensive.

ROM

Read Only Memory. In hard drives this generally refers to a specific chip, or even the code contained within the ROM chip on the PCB which is necessary to properly initialize the drive. To replace the PCB of many drives requires that the ROM be transferred either physically or electronically to the new board. For some models if this code is lost, it is impossible to recover the data. For other models the ROM code can be rebuilt using information stored within the drives service area.

Sector

Refers to the smallest increment of data storage used by a hard drive. In most drives the size of a sector is 512bytes, however newer drives have moved to a 4kb sector size to increase data density. Each sector also contains CRC error checking information so the drive always knows if the sector was read correctly.

Service Area

In hard drives the service area refers to hidden negative numbered tracks contained on the platters of a hard drive which often contain the drives internal firmware code and other code needed for operation. The service area (or SA) also contains S.M.A.R.T. information, locations of re-mapped sectors, and drive specific adaptive parameters. For many models of hard drives, if this area of the drive is severely damaged the data cannot be recovered using current technology.

Thumb Drive

Small solid state data storage devices which connect directly into a USB port of a computer. Originally they were about the size of a human thumb, however are much smaller nowadays since many manufacturers are now producing them monolithically rather than using a PCB.