XFS文件系统是硅谷图形公司(Silicon Graphics Inc,简称SGI)开发的用于IRIX(一个UNIX操作系统)的文件系统，后将XFS移植到Linux操作系统上。XFS是高级日志文件系统，其特点极具伸缩性，同时也很健壮。2000年5月XFS通过GNU通用公共许可证移植到Linux系统上，通过十多年的不断修改已经成为一款非常成熟的文件系统。在多项针对XFS的性能测试上，XFS都取得了不俗的成绩，高并发环境下甚至已经超过ext4。
一、XFS文件系统的备份与恢复
XFS文件系统提供了整个分区备份的工具xfsdump供用户使用，用户可以在不借助第三方软件的情况下对XFS文件系统上的数据实施备份。

创建XFS分区及测试文件
[root@localhost ~]# ls /dev/sd*
/dev/sda /dev/sda1 /dev/sda2 /dev/sdb
[root@localhost ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x08a5199d

Device Boot Start End Blocks Id System

Command (m for help): n
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): p
First sector (2048-41943039, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +1G
Partition 1 of type Linux and of size 1 GiB is set

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x08a5199d

Device Boot Start End Blocks Id System
/dev/sdb1 2048 2099199 1048576 83 Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only.
[root@localhost ~]# ls /dev/sd*
/dev/sda /dev/sda1 /dev/sda2 /dev/sdb /dev/sdb1
[root@localhost ~]# mkfs.xfs -f /dev/sdb1
meta-data=/dev/sdb1 isize=512 agcount=4, agsize=65536 blks

     =                       sectsz=512   attr=2, projid32bit=1
     =                       crc=1        finobt=0, sparse=0

data = bsize=4096 blocks=262144, imaxpct=25

     =                       sunit=0      swidth=0 blks

naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=2560, version=2

     =                       sectsz=512   sunit=0 blks, lazy-count=1

realtime =none extsz=4096 blocks=0, rtextents=0
[root@localhost ~]# blkid /dev/sdb1
/dev/sdb1: UUID="61a5e59d-92d3-458d-ac09-7d945469cda6" TYPE="xfs"
[root@localhost ~]# mkdir /file
[root@localhost ~]# echo "/dev/sdb1 /file xfs defaults 0 0" >> /etc/fstab
[root@localhost ~]# mount -a
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/rhel-root 17G 1.9G 16G 12% /
devtmpfs 901M 0 901M 0% /dev
tmpfs 912M 0 912M 0% /dev/shm
tmpfs 912M 8.7M 903M 1% /run
tmpfs 912M 0 912M 0% /sys/fs/cgroup
/dev/sr0 3.8G 3.8G 0 100% /yum
/dev/sda1 1014M 143M 872M 15% /boot
tmpfs 183M 0 183M 0% /run/user/0
/dev/sdb1 1014M 33M 982M 4% /file
[root@localhost ~]# cd /file/
[root@localhost file]# ls
[root@localhost file]# touch file{1..100}
[root@localhost file]# ls
file1 file16 file23 file30 file38 file45 file52 file6 file67 file74 file81 file89 file96
file10 file17 file24 file31 file39 file46 file53 file60 file68 file75 file82 file9 file97
file100 file18 file25 file32 file4 file47 file54 file61 file69 file76 file83 file90 file98
file11 file19 file26 file33 file40 file48 file55 file62 file7 file77 file84 file91 file99
file12 file2 file27 file34 file41 file49 file56 file63 file70 file78 file85 file92
file13 file20 file28 file35 file42 file5 file57 file64 file71 file79 file86 file93
file14 file21 file29 file36 file43 file50 file58 file65 file72 file8 file87 file94
file15 file22 file3 file37 file44 file51 file59 file66 file73 file80 file88 file95
备份XFS分区
[root@localhost file]# mkdir /backup
[root@localhost file]# yum install -y xfsdump
[root@localhost file]# xfsdump -f /backup/file.bak /file

利用xfsdump备份挂载点/file对应的分区

xfsdump: using file dump (drive_simple) strategy
xfsdump: version 3.1.4 (dump format 3.0) - type ^C for status and control

============================= dump label dialog ==============================

输入dump会话标签

please enter label for this dump session (timeout in 300 sec)
-> file.bak
session label entered: "file.bak"

--------------------------------- end dialog ---------------------------------

xfsdump: level 0 dump of localhost.localdomain:/file
xfsdump: dump date: Thu Oct 31 22:16:02 2019
xfsdump: session id: 02a1445f-5ff3-4518-ab2c-888d9e2a4c44
xfsdump: session label: "file.bak"
xfsdump: ino map phase 1: constructing initial dump list
xfsdump: ino map phase 2: skipping (no pruning necessary)
xfsdump: ino map phase 3: skipping (only one dump stream)
xfsdump: ino map construction complete
xfsdump: estimated dump size: 52800 bytes

============================= media label dialog =============================

输入媒体标签

please enter label for media in drive 0 (timeout in 300 sec)
-> file
media label entered: "file"

--------------------------------- end dialog ---------------------------------

xfsdump: creating dump session media file 0 (media 0, file 0)
xfsdump: dumping ino map
xfsdump: dumping directories
xfsdump: dumping non-directory files
xfsdump: ending media file
xfsdump: media file size 86544 bytes
xfsdump: dump size (non-dir files) : 0 bytes
xfsdump: dump complete: 27 seconds elapsed
xfsdump: Dump Summary:
xfsdump: stream 0 /backup/file.bak OK (success)
xfsdump: Dump Status: SUCCESS
[root@localhost file]# ls /backup/

已经成功创建备份文件

file.bak
恢复过程
[root@localhost file]# ls
file1 file16 file23 file30 file38 file45 file52 file6 file67 file74 file81 file89 file96
file10 file17 file24 file31 file39 file46 file53 file60 file68 file75 file82 file9 file97
file100 file18 file25 file32 file4 file47 file54 file61 file69 file76 file83 file90 file98
file11 file19 file26 file33 file40 file48 file55 file62 file7 file77 file84 file91 file99
file12 file2 file27 file34 file41 file49 file56 file63 file70 file78 file85 file92
file13 file20 file28 file35 file42 file5 file57 file64 file71 file79 file86 file93
file14 file21 file29 file36 file43 file50 file58 file65 file72 file8 file87 file94
file15 file22 file3 file37 file44 file51 file59 file66 file73 file80 file88 file95
[root@localhost file]# rm -rf *
[root@localhost file]# ls
[root@localhost file]# xfsrestore -f /backup/file.bak /file
xfsrestore: using file dump (drive_simple) strategy
xfsrestore: version 3.1.4 (dump format 3.0) - type ^C for status and control
xfsrestore: searching media for dump
xfsrestore: examining media file 0
xfsrestore: dump description:
xfsrestore: hostname: localhost.localdomain
xfsrestore: mount point: /file
xfsrestore: volume: /dev/sdb1
xfsrestore: session time: Thu Oct 31 22:16:02 2019
xfsrestore: level: 0
xfsrestore: session label: "file.bak"
xfsrestore: media label: "file"
xfsrestore: file system id: 61a5e59d-92d3-458d-ac09-7d945469cda6
xfsrestore: session id: 02a1445f-5ff3-4518-ab2c-888d9e2a4c44
xfsrestore: media id: 2d1d9f33-dff3-4cfa-a2f6-bf65bd8f242b
xfsrestore: using online session inventory
xfsrestore: searching media for directory dump
xfsrestore: reading directories
xfsrestore: 1 directories and 100 entries processed
xfsrestore: directory post-processing
xfsrestore: restoring non-directory files
xfsrestore: restore complete: 0 seconds elapsed
xfsrestore: Restore Summary:
xfsrestore: stream 0 /backup/file.bak OK (success)
xfsrestore: Restore Status: SUCCESS
[root@localhost file]# ls

已经成功恢复被删除的文件

file1 file16 file23 file30 file38 file45 file52 file6 file67 file74 file81 file89 file96
file10 file17 file24 file31 file39 file46 file53 file60 file68 file75 file82 file9 file97
file100 file18 file25 file32 file4 file47 file54 file61 file69 file76 file83 file90 file98
file11 file19 file26 file33 file40 file48 file55 file62 file7 file77 file84 file91 file99
file12 file2 file27 file34 file41 file49 file56 file63 file70 file78 file85 file92
file13 file20 file28 file35 file42 file5 file57 file64 file71 file79 file86 file93
file14 file21 file29 file36 file43 file50 file58 file65 file72 file8 file87 file94
file15 file22 file3 file37 file44 file51 file59 file66 file73 file80 file88 file95
二、XFS文件系统的检查和修复
创建XFS测试分区
[root@localhost file]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x08a5199d

Device Boot Start End Blocks Id System
/dev/sdb1 2048 2099199 1048576 83 Linux

Command (m for help): n
Partition type:
p primary (1 primary, 0 extended, 3 free)
e extended
Select (default p): p
Partition number (2-4, default 2):
First sector (2099200-41943039, default 2099200):
Using default value 2099200
Last sector, +sectors or +size{K,M,G} (2099200-41943039, default 41943039): +1G
Partition 2 of type Linux and of size 1 GiB is set

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x08a5199d

Device Boot Start End Blocks Id System
/dev/sdb1 2048 2099199 1048576 83 Linux
/dev/sdb2 2099200 4196351 1048576 83 Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
[root@localhost file]# partprobe
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only.
[root@localhost file]# ls /dev/sd*
/dev/sda /dev/sda1 /dev/sda2 /dev/sdb /dev/sdb1 /dev/sdb2
[root@localhost file]# mkfs.xfs /dev/sdb2
meta-data=/dev/sdb2 isize=512 agcount=4, agsize=65536 blks

     =                       sectsz=512   attr=2, projid32bit=1
     =                       crc=1        finobt=0, sparse=0

data = bsize=4096 blocks=262144, imaxpct=25

     =                       sunit=0      swidth=0 blks

naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=2560, version=2

     =                       sectsz=512   sunit=0 blks, lazy-count=1

realtime =none extsz=4096 blocks=0, rtextents=0
检查XFS文件系统，如果检查过程中发现问题将会列出
[root@localhost file]# xfs_repair -n /dev/sdb2
Phase 1 - find and verify superblock...
Phase 2 - using internal log

    - zero log...
    - scan filesystem freespace and inode maps...
    - found root inode chunk

Phase 3 - for each AG...

    - scan (but don't clear) agi unlinked lists...
    - process known inodes and perform inode discovery...
    - agno = 0
    - agno = 1
    - agno = 2
    - agno = 3
    - process newly discovered inodes...

Phase 4 - check for duplicate blocks...

    - setting up duplicate extent list...
    - check for inodes claiming duplicate blocks...
    - agno = 0
    - agno = 1
    - agno = 2
    - agno = 3

No modify flag set, skipping phase 5
Phase 6 - check inode connectivity...

    - traversing filesystem ...
    - traversal finished ...
    - moving disconnected inodes to lost+found ...

Phase 7 - verify link counts...
No modify flag set, skipping filesystem flush and exiting.
自动检查并修复XFS文件系统
[root@localhost file]# xfs_repair /dev/sdb2
Phase 1 - find and verify superblock...
Phase 2 - using internal log

    - zero log...
    - scan filesystem freespace and inode maps...
    - found root inode chunk

Phase 3 - for each AG...

    - scan and clear agi unlinked lists...
    - process known inodes and perform inode discovery...
    - agno = 0
    - agno = 1
    - agno = 2
    - agno = 3
    - process newly discovered inodes...

Phase 4 - check for duplicate blocks...

    - setting up duplicate extent list...
    - check for inodes claiming duplicate blocks...
    - agno = 0
    - agno = 1
    - agno = 2
    - agno = 3

Phase 5 - rebuild AG headers and trees...

    - reset superblock...

Phase 6 - check inode connectivity...

    - resetting contents of realtime bitmap and summary inodes
    - traversing filesystem ...
    - traversal finished ...
    - moving disconnected inodes to lost+found ...

Phase 7 - verify and correct link counts...
done