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1.1 Glossary

The following terms are defined in [MS-GLOS]:

8.3 name
Access Control List (ACL)
binary large object (BLOB)
Distributed Link Tracking (DLT)
FAT file system
file stream
globally unique identifier (GUID)
logical cluster number (LCN)
named stream
NetBIOS name
object identifier (OID)
replica set
security identifier (SID)
single-instance storage (SIS)
symbolic link
Unicode character
Universal Disk Format (UDF)
Uniform Resource Locator (URL)
update sequence number (USN)

The following terms are specific to this document:

alternate name: An 8.3 name that can optionally be generated when a file is created. A file will not have an alternate name if the user wants to optimize performance, or if the name of the file already uses the 8.3 format.

chunk: The amount of data that the operating system's implementation of the Lempel-Ziv compression algorithm tries to compress at one time. The compression unit size used by the file system is always a multiple of the underlying compression algorithm's chunk size. For more information on the Lempel-Ziv compression algorithm, see [UASDC].

cluster: The smallest allocation unit on a volume.

compression unit: The amount of data that NTFS tries to compress at one time. Compression of large files is accomplished as a series of compressions of data blocks, each at the most compression unit bytes in size.

compression unit shift: The number of bits by which to left-shift a 1 bit to arrive at the compression unit size.

content indexing service: A Windows service that extracts content from files and constructs an indexed catalog to facilitate efficient and rapid searching.

disk quota: Maximum amount of data a user may store on a disk volume.

dot directory name: In a pathname, a directory name component of "." or "..". For more details, see section

file name component: The portion of a file name between path separator characters (or backslashes).

file record segment: A record in the master file table that contains attributes for a specific file on an NTFSvolume. The file record segment is always 1,024 bytes (1 kilobyte) in size.

filter: Type of driver that is layered between the kernel and a base file system (such as FAT or NTFS) that receives I/O request packets on their way to and from the base file system. The term filter can refer to legacy filters or minifilters.

filter manager: A file system filter driver that simplifies the development of other file system filter drivers. Although it is possible to write a filter driver that manages other filters, for the purposes of this document, the phrase filter manager refers only to the file system filter manager, which is an operating system component. A filter driver developed to the filter manager model is called a minifilter.

independent software vendor (ISV): A company or organization that develops software solutions that may utilize this specification.

legacy filter: A file system filter that does not work with the Windows file system filter manager.

master file table (MFT): On an NTFSvolume, the MFT is a relational database that consists of rows of file records and columns of file attributes. It contains at least one entry for every file on an NTFSvolume, including the MFT itself. The MFT stores the information required to retrieve files from the NTFSpartition.

master file table mirror (MFT2/MFTMirr): On an NTFSvolume, the MFT2 is a redundant copy of the first four (4) records of the MFT.

minifilter: A file system filter developed to work with the file system filter manager.

object-oriented file system: In the context of file system control codes, a file system that allows the assignment of object IDs to files.

Offload Read: A variant to a normal read operation where a target device generates and returns a Token instead of a buffer containing the data to be read. The Token is maintained by the target device until it invalidates the Token for any vendor-specific reason. The data logically represented by the Token cannot change, and the target device is required to maintain this representation. An example of a target device is a SAN Storage Array with support for the associated low-level storage commands. For more information on Offload Read, see [INCITS-T10/11-059].

Offload Write: A variant to a normal write operation where the host provides a Token instead of a buffer containing the data to be written. Upon receipt of the Offload Write, the target device parses the Token and determines whether the data movement (the Write) can be completed to the requested location. An example of a target device is a SAN Storage Array with support for the associated low-level storage commands. For more information on Offload Write, see [INCITS-T10/11-059].

ReparseGuid: A 16-byte GUID that uniquely identifies the owner of the reparse point. Reparse pointGUIDs are assigned by the implementer of a file system, the file system filter driver, or the minifilter driver. The implementer must generate one GUID to use with their assigned reparse point tag, and must always use this GUID as the ReparseGuid for that tag.

reparse point: An attribute that can be added to a file to store a collection of user-defined data that is opaque to NTFS or ReFS. If a file that has a reparse point is opened, the open will normally fail with STATUS_REPARSE, so that the relevant file system filter driver can detect the open of a file associated with (owned by) this reparse point. At that point, each installed filter driver can check to see if it is the owner of the reparse point, and, if so, perform any special processing required for a file with that reparse point. The format of this data is understood by the application that stores the data and the file system filter that interprets the data and processes the file. For example, an encryption filter that is marked as the owner of a file's reparse point could look up the encryption key for that file. A file can have (at most) 1 reparse point associated with it.

reparse point tag: A unique identifier for a file system filter driver stored within a file's optional reparse point data that indicates the file system filter driver that performs additional filter-defined processing on a file during I/O operations. An implementer may request more than one reparse point for use with a file system, a file system filter driver, or a minifilter driver. To request a reparse point tag, use the reparse point tag request form. For more information, see [WHDC-RPTR].

short name: This has the same definition as alternate name.

sparse file: A file containing large sections of data composed only of zeros, which is marked as such in the NTFS. The file system saves disk space by only allocating as many ranges on disk as are required to completely reconstruct the nonzero data. When an attempt is made to read in the non-allocated portions of the file (also known as holes), the file system automatically returns zeros to the caller.

sub-read and sub-write: An I/O operation sent by the file system to the storage stack that is part of a larger file I/O operation. Sometimes large file reads and writes are broken down by the file system into smaller reads and writes, which are then sent to the storage stack.

tag: Another name for a reparse point. For instance, the file system filter manager FltTagFile routine sets a reparse point on a file. Tag is also used to refer to the field in a reparse point that identifies what software component put the reparse point there.

Token (for Offload Operations): A 512-byte length opaque string that is generated and maintained by a supported target device. A Token functions logically as an immutable point-in-time representation for a set of data specified by a host and can be conceptualized as a compressed representation of the data that only a certain class of storage subsystems can interpret. A Token can also be constructed from a set of well-known Tokens to enable the client to describe a homogeneous attribute for a set of data (for example, all zeros) or to enable a server to apply a homogeneous attribute to a set of data (for example, a set of all zeros). For more information on Tokens, see [INCITS-T10/11-059].

virtual cluster number (VCN): The cluster number relative to the beginning of the file, directory, or stream within a file. The cluster describing byte 0 in a file is VCN 0.

MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as specified in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.

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