How does NTFS handle data structures

NTFS (New Technology File System), the standard file system for Windows NT and its subsequent versions, utilizes various data structures to organize and manage data efficiently. Here are some key data structures NTFS employs:

1. Master File Table (MFT): This is the most crucial data structure in NTFS. MFT is like a database that stores information about all files and directories on the volume. Each file or directory entry in the MFT contains metadata such as file attributes, timestamps, security descriptors, and pointers to the data extents on the disk. MFT itself is a file, typically allocated at the beginning of the volume.

2. File Record Segments (FRS): Each entry in the MFT is called a File Record Segment (FRS). An FRS holds information about a specific file or directory. It includes metadata attributes like file name, size, timestamps, permissions, and pointers to the data extents where the actual file content is stored.

3. Data Runs: NTFS uses a technique called extent-based allocation. Rather than storing data contiguously, it stores data in non-contiguous chunks called extents. Each extent is represented as a data run, which consists of a starting cluster address and the number of clusters the extent occupies. This allows for more efficient disk space utilization and reduces fragmentation.

4. Attribute List: NTFS allows for storing extended attributes for files and directories. When the attributes exceed the space available in the MFT record, NTFS uses an attribute list to store additional attributes. The attribute list is a separate data structure that holds pointers to other MFT records containing extended attributes.

5. Bitmaps: NTFS utilizes bitmaps to manage free space and track allocated clusters on the volume. There are several bitmaps, including the volume bitmap (which tracks the allocation status of each cluster on the volume), the MFT bitmap (which tracks the allocation status of MFT entries), and others for various system structures.

6. Security Descriptors: Each file and directory in NTFS has a security descriptor associated with it. This descriptor contains information about the object's security attributes, including access control lists (ACLs) specifying which users and groups have permissions to access the object and what actions they can perform.

These data structures collectively enable NTFS to provide features like file and directory organization, efficient storage allocation, security, and fault tolerance. They play a crucial role in the functioning and performance of the file system.