Linux 14th Day Self-study btrfs and compression archive

Linux 14th Day self-study btrfs and compression archive

Time: 20180731

Btrfs

This file system is designed to address the scalability requirements of large machines for file systems. Find files when directory files become more

The retrieval capability will not grow linearly with data consistency, snapshot backup data, etc.

Characteristics

1. All metadata in this filesystem are managed by the Btree algorithm, with the advantage of finding, inserting, and deleting

Efficient operation.

2. The filesystem uses extent instead of block to manage the disk, extent is a contiguous block, a

The extent is customized by the starting block plus the length.

Extent can effectively reduce metadata overhead, in order to manage disk space, the file system needs to know which blocks

is free. The Ext file system uses each bit in the bitmap to correspond to a block on the disk when the corresponding

After the block is allocated, the corresponding bit in the bitmap is set to 1. It's a classic and very clear design.

Unfortunately, when the capacity of the disk becomes larger, the space occupied by the bitmap itself becomes larger. This leads to a

Scalability issues, as the capacity of the storage device increases, the bit of this metadata occupies more space.

And people hope that no matter how disk capacity increases, the metadata should not increase linearly with it. In Btrfs, the

Only one meta-data is required. For large files, extent shows relatively superior management performance.

3. Dynamic Inode allocation, before file system initialization has already fixed the inode of the system, thus restricting this

The maximum number of files stored by the file system, while in Btrfs users can insert new

Inode, where the physical storage location is dynamically allocated. So Btrfs doesn't have a limit on the number of files.

4. Data consistency features cow transactions, checksum

5. Multi-Device management-related feature snapshots and cloning soft raid

6. Delay allocation

7. Inline file when the data file is too small to be stored in the same extent as the source data

8. Btrfs now has an important drawback when a node in the Btree error occurs, the filesystem loses

All the file information under the node.

Introduction to Btrfs Usage

Creating a file system

Mkfs.btrfs/dev/sda8

Partx-a/DEV/SDA

Mkdir/mnt/btrfs

Mount-t Btrfs/dev/sda8/mnt/btrfs

You can use Df-i to view its inode status, which displays unlimited

As this system is still in development, the author himself also learned not fine, currently only introduced here.

Compression and decompression of Linux system files

Compression Decompression Tool

The Gzip/gunzip command corresponds to a compressed format file that ends in. gz

The BZIP2/BUNZIP2 command corresponds to a compressed format file that ends in. bz2

Xz/unxz it corresponds to the. XZ end of the compressed format file

Zip/unzip it corresponds to a compressed format file at the end of the. zip

Gzip/gunzip

gzip [-ACDFHLLNNRTVV19] [-s suffix] [name ...]

Gunzip [-ACFHLLNNRTVV] [-s suffix] [name ...]

Zcat [-FHLV] [name ...]

-# indicates a compression ratio of 1-9, the default is 6, the higher the number the higher the compression rate

-D Decompress uncompress decompression

-C retains the original data and outputs the compressed data to the standard output

such as Gzip-c/path/files >/path/file.gz

-R recursive recursively to the directory to compress each file

zcat/path/file.gz To view the contents of a compressed file without explicit decompression

Bzip2/bunzip2

bzip2 [-cdfkqstvzvl123456789] [filenames ...]

BUNZIP2 [-FKVSVL] [filenames ...]

Bzcat [-S] [filenames ...]

Bzip2recover filename

-# 1-9 Default to 6 specifies compression ratio

-D decompress equivalent to BUNZIP2

-K to retain the original file after compression

bzcat/path/file.bz2 to view compressed file content without explicit decompression

Xz/unxz

-# indicating compression ratio

-D decompress equivalent to UNXZ

-K Do not delete the original file

Xzcat/path/file.xz To view the contents of a compressed file without explicit decompression

Zip/unzip

Zip File.zip/path/files

Archiving tools

Archiving is the packaging of multiple files into a single file for easy administration, and the default archive does not perform compression

Common tools are tar, Cpio

Tar Archive compression Tool

Archive

Tar-c-f/path/file.tar/path/file

Note: The archive does not delete the original file

Expand Archive

Tar-xf/path/fiole.tar [-c/path/dir]

View a list of archived files

Tar-t-f/path/tarfile.tar

Archive Plus Compress

TAR-ZCF File.tar.gzip/path/files

TAR-ZXF File.tar.gzip

TAR-JCF File.tar.bzip2/path/files

TAR-JXF FILE.TAR.BZIP2

TAR-JCF File.tar.xz/path/files

TAR-JXF FILE.TAR.XZ

Note: You can use TAR-XF file to expand the archive without specifying the compression tool option

Linux 14th Day Self-study btrfs and compression archive