Explanation of basic knowledge points of file system

1. File system overview

1. The file system is based on the operating system and is used to manage and organize the data stored on the disk drive. Through the data storage layout/space management/file Management of naming/security control and other aspects solves how to effectively store data on the device.

2. The file system is a bridge between the operating system and the disk device. The file system realizes the rational organization and effective access of data, which is reflected in the management of files and directories on the operating system.

3. Metadata: In addition to saving and managing data stored in files, the file system also stores some important information about files and the file system itself (such as file permissions/size/owner, etc.) to the disk. , this information is called the metadata of the file system

4. File system usage process:

1. Storage media selection: such as hard disk/network storage, etc.

2. Disk partitioning: use partitioning tools such as fdisk/cfdisk/parted

3. File system creation: Command: mkfs

Syntax: mkfs [-v] [-t fstype] Device

• -v Display version information of mkfs

• - t fstype: Specify the file system type to be created. If this option is not added, the default is the ext2 file system

• Device: The disk or disk partition to be formatted

Example: mkfs -t ext3

4. Mount device: The process of associating a file system with a storage is called mounting.

二.ext3 and ext4 file systems

1. Introduction: The most commonly used file systems in Linux: ext2/ext3/ext4/ReiserFS/XFS. Linux standard files start with VFS, then ext--ext2--ext3.

2.ext2 is a standard file system on Linux.

3.ext3 file system

is a log file system , in fact, it is to add a special incode (log file) based on the ext2 file system, that is, the logging function. Depending on the implementation technology of the log file system, ext3 provides three log modes:

• journal mode: All data and metadata changes in the file system are written to the log. The safest and slowest.

• Ordered mode: Only modifications to file system metadata will be logged. Default mode.

• Writeback mode: metadata is updated first, and then the data is updated. fastest.

4.ext4 file system features:

• Supports more subdirectories: Theoretically, an unlimited number is supported.

• Supports larger file systems and larger files: the file system capacity reaches 1EB and the file capacity reaches 16TB.

• Support partition structure

• Support log verification

• Support fast fsck

• Support online defragmentation

5.ReiserFs

Manage data through a fully balanced structure, including file data/file name and log support etc. The features are as follows:

• Efficient and reasonable utilization of disk space

• Advanced log management mechanism

• Unique search method: Search method based on fast balanced tree

• Supports massive disk storage

If the application system has many small files, at the same time With a lot of read/write operations, the ReiserFS file system is definitely the first choice.

6.XFS

(1) Features:

• Excellent logging function

• can Strong scalability

• Fast writing performance

(2) Use

• file system Formatting command: mkfs.xfs

• File system defragmentation command: xfs_fsr

• ##xfs_bmap: View file block status

• xfs_db: Check disk fragmentation

• xfs_fsr: Defragment

• File system consistency Detection: xfs_repair

three. File system selection criteria

1. Applications with frequent read operations and numerous small files: Selection suggestions: ext4--xfs--ext3.

2. Frequent write operations: XFS--ext4--ext3

3. The performance/security requirements are not high: ext2

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