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File Protection and Security

In the file system, file protection and file confidentiality are important measures to ensure data security.

  • File protection: Prevent user errors from causing file data loss or damage.
  • File confidentiality: Prevent unauthorized users from accessing file contents.

Factors affecting file system security

  • Human factors: Misoperation, malicious attacks, abuse of permissions, etc.
  • System factors: Hardware failure, software vulnerabilities, system crashes, etc.
  • Natural factors: Power failure, natural disasters (such as fire, earthquake), etc.

Main measures for file system security

  • Access control mechanism: Limit user access rights to files to prevent misoperation or malicious operations.
  • Disk fault tolerance technology: Prevent data loss caused by system failures by increasing redundancy and backup.
  • Backup technology: Regularly back up data to other storage devices to prevent data loss caused by natural factors.

Access control

Access control is to limit user operations on files by setting file access rights, which can both protect files and ensure the confidentiality of files.

Common file access permissions

Permissions Description
E Executable
R Readable
W Writable
- No permissions

Access control scheme

  • Access control matrix: Describes the access permission relationship between users and files through a two-dimensional matrix. Rows represent users, columns represent files, and each element of the matrix represents the user's operation permission on the file.

  • Access control table: Each file corresponds to a table that records users with access permissions and their corresponding permissions.

  • Set password: The file owner sets an access password for the file, and the user needs to provide the correct password when accessing the file.

  • File encryption: Encode the file content, and the file content can only be accessed after decryption.

Disk fault tolerance technology

Disk fault tolerance technology improves the integrity and reliability of the file system by adding redundant devices (such as disk drives and disk controllers), and is divided into the following three levels:

Level 1 fault tolerance technology

  • Applicable scenarios: Local defects occur on the disk surface.
  • Common methods:
  • Dual directories: Maintain two directory copies for the file system.
  • Dual file allocation tables: Create redundant copies for the file allocation table.
  • Hot repair redirection: Dynamically adjust the storage location of data to bypass damaged areas.
  • Read after write verification: Read the verification immediately after writing data to ensure data integrity.

Level 2 fault tolerance technology

  • Applicable scenarios: Disk drive failure.
  • Common methods:
  • Disk mirroring: Copy the data of the entire disk to another disk to achieve real-time synchronization.
  • Disk duplexing: Manage two disks through two independent disk controllers to provide higher reliability.

Level 3 fault tolerance technology

  • Applicable scenarios: High-reliability network system.
  • Common methods: Combine multiple fault-tolerant and redundancy technologies to achieve highly reliable data protection.

RAID (Redundant Array of Inexpensive Disks)

RAID is an advanced fault-tolerant technology that achieves high performance and high reliability by using multiple disks and a disk array controller. The main feature of RAID is the use of redundant storage technology, which will not cause data loss even if one of the disks is damaged.

  • Common RAID levels:
  • RAID 0: Data striping to improve performance, but no fault tolerance.
  • RAID 1: Disk mirroring to achieve data redundancy.
  • RAID 5: Distributed parity to provide performance and fault tolerance.
  • RAID 6: Dual parity to provide higher fault tolerance.
  • RAID 10: Combining RAID 1 and RAID 0 to provide high performance and redundancy.

Data backup and dump

Data backup is an important measure to prevent data loss, usually achieved by copying important files to other storage media.

Common backup measures

  1. Create copies: Create multiple copies of important files and save them on different storage media (such as hard disks, CDs, USB flash drives, etc.).
  2. Periodic dump: Dump files to other storage devices regularly or periodically. Common dump methods include:
  3. Full dump: Back up all files.
  4. Incremental dump: Back up only files that have been modified since the last dump.