Glossary

It's a repertoire of character encoding that include (most of) the original 96 ASCII character set, plus up to 128 additional characters.

Apple File System is a proprietary file system developed and deployed by Apple Inc. for macOS Sierra (10.12.4) and later, iOS 10.3, tvOS 10.2, watchOS 3.2, and all versions of iPadOS. APFS is optimized for solid-state drive storage and supports encryption, snapshots, and increased data integrity, among other capabilities.

An acronym for American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. The ASCII standard is a seven-bit code with no parity guidelines, containing 128 code positions.

Boot Configuration Data. Firmware-independent database for boot-time configuration data. It is used by Microsoft's new Windows Boot Manager and replaces the boot.ini that was used by NTLDR.

Basic Input Output Subsystem is the program a personal computer's microprocessor uses to get the computer system started after you turn it on. It also manages data flow between the computer's operating system and attached devices such as the hard disk, video adapter, keyboard, mouse and printer. A typical method to access the BIOS settings screen is to press Delete / F1 / F2 / F8 / F10 or Esc during the boot sequence.

Blu-ray (Blu-ray Disc or BD) is a digital optical disc data storage format designed to supersede the DVD format. The main application of Blu-ray is as a medium for video material and for the physical distribution of video games. The name refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs, resulting in an increased capacity.

Name commonly used for the partition that contains the start-up files.

BIOS settings allow you to run a boot sequence from a floppy drive, a hard drive, a CD/DVD/BD drive or a USB device. You may configure the order that your computer searches these physical devices for the boot sequence. The first device in the order list has the first boot priority. For example, to boot from a CD/DVD/BD drive instead of a hard drive, place the CD/DVD/BD drive ahead of the hard drive in priority.

A computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager, developed together. It was created by Chris Mason in 2007 for use in Linux, and since November 2013, the file system's on-disk format has been declared stable in the Linux kernel. BtrFS is intended to address the lack of pooling, snapshots, checksums, and integral multi-device spanning in Linux file systems.

The compact disc (CD) is a digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio standard and is capable of holding of uncompressed stereo audio. In later years, the technology was adapted for computer data storage as CD-ROM and subsequently expanded into various writable and multimedia formats.

When you set a file or folder property to compress data, the file or folder uses less disk space. While the size of the file is smaller, it must use a whole cluster in order to exist on the hard drive. As a result, compressed clusters contain File Slack Space. This space may contain residual confidential data from the file that previously occupied this space. LSoft KillDisk can wipe out the residual data without touching the existing data.

A comma-separated values (CSV) file is a delimited text file that uses a comma to separate values. Each line of the file is a data record. Each record consists of one or more fields, separated by commas. The use of the comma as a field separator is the source of the name for this file format. A CSV-file typically stores tabular data (numbers and text) in plain text, in which case each line will have the same number of fields.

A cluster or allocation unit is a unit of disk space allocation for files and directories. To reduce the overhead of managing on-disk data structures, the file system does not allocate individual disk sectors by default, but contiguous groups of sectors, called clusters. A cluster is the smallest logical amount of disk space that can be allocated to hold a file. Storing small files on a file system with large clusters will therefore waste disk space; such wasted disk space is called slack space. For cluster sizes which are small versus the average file size, the wasted space per file will be statistically about half of the cluster size; for large cluster sizes, the wasted space will become greater. However, a larger cluster size reduces bookkeeping overhead and fragmentation, which may improve reading and writing speed overall. Typical cluster sizes range from 1 sector (512 B) to 128 sectors (64 Kb). The operating system keeps track of clusters in the hard disk's root records or MFT records, see Lost Cluster.

See physical device.

All disks and partitions start with a boot sector. For a damaged disk and volumes (where the location of the boot records known) the partition table can be reconstructed. The boot record contains a file system identifier.

Device node in the Local System Devices list is a physical device containing logical drives. The first physical device on older versions of Operating Systems is named 80h, now more typical name is PhysicalDrive0.

Basically the mapping of filename to its Inode. The user generally accesses the file by its name, however such filenames are not understood by the kernel. The kernel identifies a file using the inode which is unique for a file.

Set of disk attributes that specify format, partitioning etc. of a disk.

Abstraction at the user level to distinguish one disk or partition from another. For example, the path C:\WINDOWS\represents a directory WINDOWS on the partition represented by C:.

A dynamic storage made out of whole or part of physical disk to increase performance and reliability.

The DVD (digital video disc or digital versatile disc) is a digital optical disc data storage format. The medium can store any kind of digital data and has been widely used to store video programs, software and other computer files. DVDs offer significantly higher storage capacity than compact discs (CD) while having the same dimensions.

In computing, endianness is the order in which bytes within a word of digital data are transmitted over a data communication medium or addressed (by rising addresses) in computer memory, counting only byte significance compared to earliness. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). CPU may read a digital word big end first, or little end first.

Lock is applied to a partition for exclusive writing access. For example, while recovering deleted or damaged files or folders, the recovery application must have exclusive access to the target partition while recovering files. If another application or the operating system are using the target partition - the processes could interfere, so user/process must close all applications or system processes that may be using the target partition before locking it.

Extensible File Allocation Table is a file system introduced by Microsoft in 2006 and optimized for flash memory such as USB flash drives and SD cards.

The extended file system was implemented in April 1992 as the first file system created specifically for the Linux kernel. Although EXT is not a specific file system name, it has been succeeded by EXT2, EXT3 and EXT4. It has metadata structure inspired by traditional Unix filesystem principles, and was designed by Rémy Card to overcome certain limitations of the MINIX file system. It was the first implementation that used the virtual file system (VFS), for which support was added in the Linux kernel in version 0.96c, and it could handle file systems up to 2 gigabytes (GB) in size.

Second extended file system is a file system for the Linux kernel. It was initially designed by French software developer Rémy Card as a replacement for the extended file system (ext). Having been designed according to the same principles as the Berkeley Fast File System from BSD, it was the first commercial-grade filesystem for Linux. The canonical implementation of ext2 is the "ext2fs" filesystem driver in the Linux kernel. ext2 was the default filesystem in several Linux distributions, including Debian and Red Hat Linux.

Third extended file system, is a journaled file system that is commonly used by the Linux kernel. It used to be the default file system for many popular Linux distributions. Stephen Tweedie first revealed that he was working on extending ext2 in Journaling the Linux ext2fs File system in a 1998 paper, and later in a February 1999 kernel mailing list posting. The file system was merged with the mainline Linux kernel in November 2001 from 2.4.15 onward. Its main advantage over ext2 is journaling, which improves reliability and eliminates the need to check the file system after an unclean shutdown.

Fourth extended file system was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for the Lustre file system between 2003 and 2006, meant to extend storage limits and add other performance improvements. However, other Linux kernel developers opposed accepting extensions to ext3 for stability reasons, and proposed to fork the source code of ext3, rename it as ext4, and perform all the development there, without affecting existing ext3 users. This proposal was accepted, and on 28 June 2006, Theodore Ts'o, the ext3 maintainer, announced the new plan of development for ext4. A preliminary development version of ext4 was included in version 2.6.19 of the Linux kernel. On 11 October 2008, the patches that mark ext4 as stable code were merged in the Linux 2.6.28 source code repositories, denoting the end of the development phase and recommending ext4 adoption. Kernel 2.6.28, containing the ext4 file system, was finally released on 25 December 2008. On 15 January 2010, Google announced that it would upgrade its storage infrastructure from ext2 to ext4. On 14 December 2010, Google also announced it would use ext4, instead of YAFFS, on Android 2.3.

A hard disk may contain only one extended partition; the extended partition can be subdivided into multiple logical partitions. In DOS/Windows systems, each logical partition may then be assigned an additional drive letter.

Area that contains the records of every other file and directory in a FAT-formatted disk drive. The operating system needs this information to access the files. There are FAT32, FAT16 and exFAT versions. FAT file systems are still commonly found on flash disks and other memory cards and modules (including USB flash drives), as well as many portable and embedded devices. FAT is the standard file system for digital cameras per the DCF specification.

A new version of the file system FAT16 which supported an increased number of possible clusters, but could reuse most of the existing code, so that the conventional memory footprint was increased by less than 5 KB under DOS. Cluster values are represented by 32-bit numbers, of which 28 bits are used to hold the cluster number.

Each file record assigns a number, called a file index, that is used by later records to refer to the file described by this record. The described file might be the primary PL/I source file or an INCLUDEd file. Each file record specifies a literal index for the fully qualified name of the file. For an INCLUDEd file, each file record also contains the file index and source line number from where the INCLUDE request came. (For primary source files, these fields are zero.)

Set of unique file properties, that allows recognize file type. File types are recognized by specific patterns that may serve as a reference for file recovery. When a file header is damaged, the type of file may be determined by examining patterns in the damaged file and comparing these patterns to known file type templates.

The smallest file (and even an empty folder) takes up an entire cluster. A 10-byte file will take up 2,048 bytes if that is the cluster size. File slack space is the unused portion of a cluster. This space may contain residual confidential data from the file that previously occupied this space. LSoft KillDisk can wipe out the residual data without touching the existing data.

Method in which files are named and where they are placed logically for storage and retrieval in a computer. Under scope of this document, one of the Microsoft Windows file systems, such as FAT12, FAT16, FAT32 and NTFS.

A specialized table with a predefined schema that stores FILESTREAM data, as well as file and directory hierarchy information and file attributes.

File Transfer Protocol. This is a standard network protocol used for the transfer of computer files between a Client and Server on a computer network. FTP is built on a client-server model architecture using separate control and data connections between the client and the server. FTP users may authenticate themselves with a clear-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it. For secure transmission that protects the username and password, and encrypts the content, FTP is often secured with SSL/TLS (FTPS) or replaced with SSH File Transfer Protocol (SFTP). The first FTP client applications were command-line programs developed before operating systems had graphical user interfaces, and are still shipped with most Windows, Unix, and Linux operating systems. Many FTP clients and automation utilities have since been developed for desktops, servers, mobile devices, and hardware, and FTP has been incorporated into productivity applications, such as HTML editors.

A cluster that is not occupied by a file. This space may contain residual confidential data from the file that previously occupied this space. LSoft KillDisk can wipe out the residual data.

A free operating system for PC compatible computers. It intends to provide a complete DOS-compatible environment for running legacy software and supporting embedded systems. FreeDOS can be booted from a floppy disk or USB flash drive. It is designed to run well under virtualization or x86 emulation. Unlike most versions of MS-DOS, FreeDOS is composed of free and open-source software, licensed under the terms of the GNU General Public License.

A standard for the layout of partition tables of a physical computer storage device, such as a hard disk drive or solid-state drive, using universally unique identifiers (UUIDs), which are also known as globally unique identifiers (GUIDs). Forming a part of the Unified Extensible Firmware Interface (UEFI) standard (Unified EFI Forum-proposed replacement for the PC BIOS), it is nevertheless also used for some BIOSs, because of the limitations of MBR partition tables, which use 32 bits for logical block addressing (LBA) of traditional 512-byte disk sectors. GPT provides a more flexible mechanism for partitioning disks than the older MBR partitioning scheme that was common to PCs.

A hard disk drive (HDD), hard disk, hard drive, or fixed disk[a] is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnetic material.

Hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of sixteen. Hexadecimal uses sixteen distinct symbols, most often the symbols "0"–"9" to represent values 0 to 9 and "A"–"F" (or "a"–"f") to represent values from ten to fifteen.

HFS Plus (also known as Mac OS Extended or HFS Extended) is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1. HFS+ continued as the primary Mac OS X file system until it was itself replaced with the Apple File System (APFS), released with macOS High Sierra in 2017. HFS+ is also one of the formats supported by the iPod digital music player. Compared to HFS, HFS+ supports much larger files (block addresses are 32-bit length instead of 16-bit) and using Unicode (instead of Mac OS Roman or any of several other character sets) for naming items. Like HFS, HFS Plus uses B-trees to store most volume metadata, but unlike most file systems that support hard links, HFS Plus supports hard links to directories. HFS Plus permits filenames up to 255 characters in length, and n-forked files. HFS Plus also uses a full 32-bit allocation mapping table rather than HFS's 16 bits, improving the use of space on large disks.

Index node is a data structure in a Unix-style file system that describes a file-system object such as a file or a directory. Each inode stores the attributes and disk block locations of the object's data. File-system object attributes may include metadata (times of last change, access, modification), as well as owner and permission data. A directory is a list of inodes with their assigned names. The list includes an entry for itself, its parent, and each of its children.

Internet Small Computer Systems Interface. iSCSI is a transport layer protocol that works on top of the Transport Control Protocol (TCP). It enables block-level SCSI data transport between the iSCSI initiator and the storage target over TCP/IP networks.

An International Organization for Standardization ISO-9660 file system is a standard CD-ROM file system that allows you to read the same CD-ROM whether you're on a PC, Mac, or other major computer platform. Disk images of ISO-9660 file systems (ISO images) are a common way to electronically transfer the contents of CD-ROMs. They often have the file name extension .ISO (though not necessarily), and are commonly referred to as "ISO".

Journaled File System is a 64-bit journaling file system created by IBM. There are versions for AIX, OS/2, eComStation, ArcaOS and Linux operating systems. The latter is available as free software under the terms of the GNU General Public License (GPL). HP-UX has another, different filesystem named JFS that is actually an OEM version of Veritas Software's VxFS. In the AIX operating system, two generations of JFS exist, which are called JFS (JFS1) and JFS2 respectively. IBM's JFS was originally designed for 32-bit systems. JFS2 was designed for 64-bit systems. In other operating systems, such as OS/2 and Linux, only the second generation exists and is called simply JFS.

The Logical Disk Manager is an implementation of a logical volume manager for Microsoft Windows NT, developed by Microsoft and Veritas Software. It was introduced with the Windows 2000 operating system, and is supported in Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows 8, Windows 10 and Windows 11. The MMC-based Disk Management snap-in (diskmgmt.msc) hosts the Logical Disk Manager. On Windows 8 and Windows Server 2012, Microsoft deprecated LDM in favor of Storage Spaces. Logical Disk Manager enables disk volumes to be dynamic, in contrast to the standard basic volume format. Basic volumes and dynamic volumes differ in their ability to extend storage beyond one physical disk. Basic partitions are restricted to a fixed size on one physical disk. Dynamic volumes can be enlarged to include more free space - either from the same disk or another physical disk.

Partitioned space on a physical device.

A cluster that has an assigned number in the file allocation table, even though it is not assigned to any file. You can free up disk space by reassigning lost clusters. In DOS and Windows you can find lost clusters with the ScanDisk utility.

M.2 formerly known as the Next Generation Form Factor (NGFF), is a specification for internally mounted computer expansion cards and connectors. It was developed to replace the older Mini SATA (mSATA) and Mini PCIe (mPCIe) standards. M.2 supports a variety of module sizes and interface types, offering greater flexibility for modern devices. It is widely used in compact systems such as ultrabooks and tablet computers, particularly for solid-state drives (SSDs), due to its smaller size and higher performance compared to mSATA. The M.2 connector can provide multiple interface options, including up to four lanes of PCI Express, as well as Serial ATA 3.0 and USB 3.0. The supported interfaces vary depending on the device and host implementation. M.2 modules and slots use different "keying" notches to indicate supported interfaces and to prevent incompatible installations. For storage devices, M.2 supports both the older Advanced Host Controller Interface (AHCI) and the newer NVM Express (NVMe) protocols. AHCI provides compatibility with legacy SATA-based systems and operating systems, while NVMe is designed for high-speed SSDs and allows for much faster performance by supporting multiple simultaneous I/O operations.

All disks start with a boot sector. When you start the computer, the code in the MBR executes before the operating system is started. The location of the MBR is always track (cylinder) 0, side (head) 0, and sector 1. The MBR contains a file system identifier.

File that contains the records of every other file and directory in an NTFS-formatted hard disk drive. The operating system needs this information to access the files.

#NTFS supports multiple data streams where the stream name identifies a new data attribute on the file. A handle can be opened to each data stream. A data stream, then, is a unique set of file attributes. Streams have separate opportunistic locks, file locks, and sizes, but common permissions.

A structure which may contain data and connections to other nodes, sometimes called edges or links. Each node in a tree has zero or more child nodes, which are below it in the tree (by convention, trees are drawn with descendants going downwards). A node that has a child is called the child's parent node (or superior). All nodes have exactly one parent, except the topmost root node, which has none. A node might have many ancestor nodes, such as the parent's parent. Child nodes with the same parent are sibling nodes. Typically siblings have an order, with the first one conventionally drawn on the left. Some definitions allow a tree to have no nodes at all, in which case it is called empty.

New Technology File System (developed by Microsoft) is the file system that the Windows NT operating system uses for storing and retrieving files on a hard disk. NTFS is the Windows NT equivalent of the Windows 95 file allocation table (FAT (File Allocation Table)) and the OS/2 High Performance File System (HPFS). All the latest Windows Operating Systems (Windows Vista, Windows 7, Windows 10) still use NTFS as a default file system.

Aka NT loader is the boot loader for all releases of Windows NT operating system up to and including Windows XP and Windows Server 2003. NTLDR is typically run from the primary hard disk drive, but it can also run from portable storage devices such as a CD/DVD or USB flash drive.

NVM Express (NVMe) or Non-Volatile Memory Host Controller Interface Specification (NVMHCIS) is an open, logical-device interface specification for accessing a computer's non-volatile storage media usually attached via the PCI Express bus. The initial NVM stands for non-volatile memory, which is often NAND flash memory that comes in several physical form factors, including solid-state drives (SSDs), PCIe add-in cards, and M.2 cards, the successor to mSATA cards. NVM Express, as a logical-device interface, has been designed to capitalize on the low latency and internal parallelism of solid-state storage devices.

An offset denotes the number of address locations added to a base address in order to get to a specific absolute address. In this (original) meaning of offset, only the basic address unit, usually the 8-bit byte, is used to specify the offset's size. In this context an offset is sometimes called a relative address.

A Linux distribution. It is widely used throughout the world. The focus of its development is creating usable open-source tools for software developers and system administrators, while providing a user-friendly desktop and feature-rich server environment.

Hard disk's storage space divided into independent parts. Each partition can behave like a separate disk drive.

On NTFS or FAT (File Allocation Table) file systems, the partition boot sector is a small program that is executed when the operating system tries to access a particular partition. On personal computers, the Master Boot Record (MBR) uses the partition boot sector on the system partition to determine file system type, cluster size, etc., and to load the operating system kernel files. Partition boot sector is usually the first sector of the partition.

Partition schemes define how data is stored on the file system. The scheme is important because it determines how the data is queried.

A table that contains data of partitions on a disk, divided into segments, called partitions. In this table, partitions data or a map of partitions is stored and organized for users to comprehend. The common location of such data used to be the first sector when Master Boot Record (MBR) was the primary partitioning scheme in PCs. Nowadays, other more advanced formats divide a disk drive into partitions, like GUID Partition Table (GPT) or Apple partition map (APM). As for GPT, this partitioning scheme is saved in sector 2 and keeps sector 1 empty for MBR data for backward compatibility.

Device for storing data, that can be connected internally (Hard Drive) or externally (USB Flash card, USB Hard Drive).

See Disk geometry.

Preboot EXecution Environment. In computing the Preboot Execution Environment specification describes a standardized client-server environment that boots a software assembly, retrieved from a network, on PXE-enabled clients. On the client side it requires only a PXE-capable network interface controller, and uses a small set of industry-standard network protocols such as DHCP and TFTP.

RAID ("Redundant Array of Inexpensive Disks" or "Redundant Array of Independent Disks") is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, provides a different balance among the key goals: reliability, availability, performance, and capacity. RAID levels greater than RAID 0 provide protection against unrecoverable sector read errors, as well as against failures of whole physical drives.

RAID 0

RAID 0 consists of striping, but no mirroring or parity. Compared to a spanned volume, the capacity of a RAID 0 volume is the same; it is the sum of the capacities of the drives in the set. But because striping distributes the contents of each file among all drives in the set, the failure of any drive causes the entire RAID 0 volume and all files to be lost. In comparison, a spanned volume preserves the files on the unfailing drives. The benefit of RAID 0 is that the throughput of read and write operations to any file is multiplied by the number of drives because, unlike spanned volumes, reads and writes are done concurrently. The cost is increased vulnerability to drive failures—since any drive in a RAID 0 setup failing causes the entire volume to be lost, the average failure rate of the volume rises with the number of attached drives.

RAID 1

RAID 1 consists of data mirroring, without parity or striping. Data is written identically to two or more drives, thereby producing a "mirrored set" of drives. Thus, any read request can be serviced by any drive in the set. If a request is broadcast to every drive in the set, it can be serviced by the drive that accesses the data first (depending on its seek time and rotational latency), improving performance. Sustained read throughput, if the controller or software is optimized for it, approaches the sum of throughputs of every drive in the set, just as for RAID 0. Actual read throughput of most RAID 1 implementations is slower than the fastest drive. Write throughput is always slower because every drive must be updated, and the slowest drive limits the write performance. The array continues to operate as long as at least one drive is functioning.

RAID 2

RAID 2 consists of bit-level striping with dedicated Hamming-code parity. All disk spindle rotation is synchronized and data is striped such that each sequential bit is on a different drive. Hamming-code parity is calculated across corresponding bits and stored on at least one parity drive. This level is of historical significance only; although it was used on some early machines (for example, the Thinking Machines CM-2), as of 2014 it is not used by any commercially available system.

RAID 3

RAID 3 consists of byte-level striping with dedicated parity. All disk spindle rotation is synchronized and data is striped such that each sequential byte is on a different drive. Parity is calculated across corresponding bytes and stored on a dedicated parity drive. Although implementations exist, RAID 3 is not commonly used in practice.

RAID 4

RAID 4 consists of block-level striping with dedicated parity. This level was previously used by NetApp, but has now been largely replaced by a proprietary implementation of RAID 4 with two parity disks, called RAID-DP. The main advantage of RAID 4 over RAID 2 and 3 is I/O parallelism: in RAID 2 and 3, a single read I/O operation requires reading the whole group of data drives, while in RAID 4 one I/O read operation does not have to spread across all data drives. As a result, more I/O operations can be executed in parallel, improving the performance of small transfers.

RAID 5

RAID 5 consists of block-level striping with distributed parity. Unlike RAID 4, parity information is distributed among the drives, requiring all drives but one to be present to operate. Upon failure of a single drive, subsequent reads can be calculated from the distributed parity such that no data is lost. RAID 5 requires at least three disks. Like all single-parity concepts, large RAID 5 implementations are susceptible to system failures because of trends regarding array rebuild time and the chance of drive failure during rebuild. Rebuilding an array requires reading all data from all disks, opening a chance for a second drive failure and the loss of the entire array.

RAID 6

RAID 6 consists of block-level striping with double distributed parity. Double parity provides fault tolerance up to two failed drives. This makes larger RAID groups more practical, especially for high-availability systems, as large-capacity drives take longer to restore. RAID 6 requires a minimum of four disks. As with RAID 5, a single drive failure results in reduced performance of the entire array until the failed drive has been replaced. With a RAID 6 array, using drives from multiple sources and manufacturers, it is possible to mitigate most of the problems associated with RAID 5. The larger the drive capacities and the larger the array size, the more important it becomes to choose RAID 6 instead of RAID 5. RAID 10 (see Nested RAID levels) also minimizes these problems

Remote Access Service. Is any combination of hardware and software to enable the remote access tools or information that typically reside on a network of IT devices. A remote access service connects a client to a host computer, known as a remote access server. The most common approach to this service is remote control of a computer by using another device which needs internet or any other network connection.

Resilient File System, codenamed "Protogon", is a Microsoft proprietary file system introduced with Windows Server 2012 with the intent of becoming the "next generation" file system after NTFS. The key design advantages of ReFS include automatic integrity checking and data scrubbing, elimination of the need for running chkdsk, protection against data degradation, built-in handling of hard disk drive failure and redundancy, integration of RAID functionality, a switch to copy/allocate on write for data and metadata updates, handling of very long paths and filenames, and storage virtualization and pooling, including almost arbitrarily sized logical volumes (unrelated to the physical sizes of the used drives).

Highest level of organization in the Windows registry. It is a logical group of keys, subkeys, and values in the registry that has a set of supporting files loaded into memory when Windows is started or an user logs in.

This is a Directory Table that stores information about the files and directories located in the root directory. It is only used with FAT12 and FAT16, and imposes on the root directory a fixed maximum size which is pre-allocated at creation of this volume. FAT32 stores the root directory in the Data Region, along with files and other directories, allowing it to grow without such a constraint. Thus, for FAT32, the Data Region starts here.

Used in FAT file system. A table that contains the records of every other file and directory in a FAT-formatted hard disk drive. The operating system needs this information to access the files. There are FAT32, FAT16 and FAT versions.

Security Account Manager. Database file that stores users' passwords in a hashed format. Since a hash function is one-way, this provides some measure of security for the storage of the passwords. It can be used to authenticate local and remote users. Beginning with Windows 2000 SP4, Active Directory authenticates remote users.

Serial Attached SCSI (SAS) is a point-to-point serial protocol that moves data to and from computer-storage devices such as hard disk drives, solid-state drives and tape drives. SAS replaces the older Parallel SCSI. SAS uses the standard SCSI command set.

SATA (Serial AT Attachment)[a][2] is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard to become the predominant interface for storage devices.

Small Computer System Interface. A set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interfaces. SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.

The SD card is a proprietary, non-volatile, flash memory card format developed by the SD Association (SDA). They come in three physical forms: the full-size SD, the smaller miniSD (now obsolete), and the smallest, microSD. Owing to their compact form factor, SD cards have been widely adopted in a variety of portable consumer electronics, including digital cameras, camcorders, video game consoles, mobile phones, action cameras, and camera drones.

The smallest unit that can be accessed on a disk. Typically sector size is 512 or 4096 bytes.

The ATA Secure Erase command is designed to remove all user data from a drive. With an SSD without integrated encryption, this command will put the drive back to its original out-of-box state. This will initially restore its performance to the highest possible level and the best (lowest number) possible write amplification, but as soon as the drive starts garbage collecting again the performance and write amplification will start returning to the former levels. Drives which encrypt all writes on the fly can implement ATA Secure Erase in another way. They simply zeroize and generate a new random encryption key each time a secure erase is done. In this way the old data cannot be read anymore, as it cannot be decrypted. Some drives with an integrated encryption will physically clear all blocks after that as well, while other drives may require a TRIM command to be sent to the drive to put the drive back to its original out-of-box state (as otherwise their performance may not be maximized).

SSD disk is blocked (frozen) by BIOS. The reasons can differ. Modern ATA hard drives and SSDs offer security options that help user to control access and reliably destroy data if necessary. Brand new HDD or SSD from a store have all the security features initially disabled... BIOS of many motherboards run the SECURITY_FREEZE_LOCK ATA command when booting to provide protection against manipulation.

A series of dynamic drives linked together to make one contiguous spanned volume.

Self-Monitoring, Analysis and Reporting Technology; often written as SMART is a monitoring system included in computer hard disk drives (HDDs), solid-state drives (SSDs) and embedded MultiMediaCards (eMMC) drives. Its primary function is to detect and report various indicators of drive reliability with the intent of anticipating imminent hardware failures. When SMART data indicates a possible imminent drive failure, software running on the host system may notify the user so preventative action can be taken to prevent data loss and the failing drive can be replaced and data integrity maintained.

A solid-state drive (SSD) is a type of solid-state storage device that uses integrated circuits to store data persistently. It is sometimes called semiconductor storage device, solid-state device, or solid-state disk.

A segment of metadata describing the file system on a block device, as in the Unix File System

Name commonly used for the partition that contains the operating system files.

File types are recognized by specific patterns that may serve as a reference for file recovery. When a file header is damaged, the type of file may be determined by examining patterns in the damaged file and comparing these patterns to known file type templates. This same pattern-matching process can be applied to deleted or damaged partitions. Using FAT (File Allocation Table) or NTFS templates, recovery software can assume that a particular sector is a FAT or NTFS boot sector because parts of it match a known pattern.

A minimal Linux kernel based operating system focusing on providing a base system functionality. The distribution is notable for its small size (11 to 16 MB) and minimalism; additional functions are provided by extensions. Tiny Core Linux is free and open source software and is licensed under the GNU General Public License version 2.

Tracks are concentric circles around the disk and the sectors are segments within each circle.

U.2 formerly known as SFF-8639, is a computer interface standard used to connect solid-state drives (SSDs) to a computer. It defines the physical connector, electrical characteristics, and supported communication protocols. U.2 was developed for the enterprise storage market and is designed to support multiple types of drives, including those using PCI Express (typically with NVM Express), as well as SAS and SATA. The interface supports up to four PCIe lanes and two SATA lanes, enabling high data transfer rates while maintaining compatibility with existing drive technologies.

Unified Extensible Firmware Interface is a specification for a software program that connects a computer's firmware to its operating system (OS). UEFI is expected to eventually replace BIOS. Like BIOS, UEFI is installed at the time of manufacturing and is the first program that runs when a computer is turned on.

The Unix file system is a family of file systems supported by many Unix and Unix-like operating systems. It is a distant descendant of the original filesystem used by Version 7 Unix.

Space on a hard disk where no partition exists. A partition may have been deleted or damaged or a partition may not have been created.

Text encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized.

Applicable to NTFS file system on Windows. The performance of the computer system depends a lot on the performance of the MFT. When you delete files, the MFT entry for that file is not deleted, it is marked as deleted. This is called unused space in the MFT. If unused space is not removed from the MFT, the size of the table could grow to a point where it becomes fragmented, affecting the performance of the MFT and possibly the performance of the computer. This space may also contain residual confidential data (file names, file attributes, resident file data) from the files that previously occupied these spaces. Active@ KillDisk can wipe out the residual data without touching the existing data.

A flash drive (also thumb drive, memory stick, and pen drive/pendrive) is a data storage device that includes flash memory with an integrated USB interface. A typical USB drive is removable, rewritable, and smaller than an optical disc, and usually weighs less than 30 g (1 oz).

Software layer that sits above assembled physical disks that were part of a hardware RAID system.

A virtual copy of a volume (logical drive) using a defined geometry that emulates a real logical drive or partition.

A virtual copy of a physical disk using a defined disk geometry that uses real physical disk as a source but access it.

See Virtual Disk Array

A fixed amount of storage on a hard disk. A physical device may contain a number of volumes. It is also possible for a single volume to span to a number of physical devices.

First sector of a data storage device that has not been partitioned, or the first sector of an individual partition on a data storage device that has been partitioned. It contains code to load and invoke the operating system (or other standalone program) installed on that device or within that partition.

It contains information about the volume as a whole, including the location of other key structures in the volume. The volume header is always located at 1024 bytes from the start of the volume. A copy of the volume header, the alternate volume header, is stored starting 1024 bytes before the end of the volume.

Shadow Copy (also known as Volume Snapshot Service, Volume Shadow Copy Service or VSS) is a technology included in Microsoft Windows that can create backup copies or snapshots of computer files or volumes, even when they are in use. It is implemented as a Windows service called the Volume Shadow Copy service.

Windows reserves a specified amount of volatile memory for file system operations. This is done in RAM because it is the quickest way to do these repetitive tasks.

The Windows logs keeps track of almost everything that happens in Windows OS. This enhances performance of the computer when doing repetitive tasks. Over time, these records can take up a lot of space.

WinPE is a compact Windows-based operating system used as a recovery environment to install, deploy, and repair Windows Desktop Editions, Windows Server, and other Windows operating systems. After boot to WinPE, user can:

• Set up a hard drive before installing Windows.
• Install Windows by using apps or scripts from a network or a local drive.
• Capture and apply Windows images.
• Modify the Windows operating system while it's not running.
• Set up automatic recovery tools.
• Recover data from unbootable devices.
• Add a custom shell or GUI to automate these kinds of tasks.

A high-performance 64-bit journaling file system created by Silicon Graphics, Inc (SGI) in 1993. It was the default file system in SGI's IRIX operating system starting with its version 5.3. XFS was ported to the Linux kernel in 2001; as of June 2014, XFS is supported by most Linux distributions; Red Hat Enterprise Linux uses it as its default file system. XFS excels in the execution of parallel input/output (I/O) operations due to its design, which is based on allocation groups (a type of subdivision of the physical volumes in which XFS is used- also shortened to AGs). Because of this, XFS enables extreme scalability of I/O threads, file system bandwidth, and size of files and of the file system itself when spanning multiple physical storage devices. XFS ensures the consistency of data by employing metadata journaling and supporting write barriers. Space allocation is performed via extents with data structures stored in B+ trees, improving the overall performance of the file system, especially when handling large files. Delayed allocation assists in the prevention of file system fragmentation; online defragmentation is also supported.