Linux 基础入门 08

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一、LVM（逻辑卷管理器）

逻辑卷管理器是Linux系统用于对硬盘分区进行管理的一种机制，理论性较强，其创建初衷是为了解决硬盘设备在创建分区后不易修改分区大小的缺陷。尽管对传统的硬盘分区进行强制扩容或缩容从理论上来讲是可行的，但是却可能造成数据的丢失。而LVM技术是在硬盘分区和文件系统之间添加了一个逻辑层，它提供了一个抽象的卷组，可以把多块硬盘进行卷组合并。这样一来，用户不必关心物理硬盘设备的底层架构和布局，就可以实现对硬盘分区的动态调整。

物理卷处于LVM中的最底层，可以将其理解为物理硬盘、硬盘分区或者RAID磁盘阵列，这都可以。卷组建立在物理卷之上，一个卷组可以包含多个物理卷，而且在卷组创建之后也可以继续向其中添加新的物理卷。逻辑卷是用卷组中空闲的资源建立的，并且逻辑卷在建立后可以动态地扩展或缩小空间。这就是LVM的核心理念。

二、部署逻辑卷

常用的LVM部署命令

我们在日常工作中，对卷组的管理是必须要掌握的

LVM（ logical volume manager ）是Linux环境下，对磁盘分区进行管理的一个机制，保证零停机前提下，对文件系统的大小进行调整，实现文件跨越不同的磁盘和分区，LVM提供了一个完美的解决方案

PP：物理分区 用来存储数据的块设备，可以是分区，可以是磁盘，RAID，SAN

PV：物理卷 LVM的基础逻辑块，但是和基本的物理介质（磁盘，分区）不同，包含了LVM的管理参数

VG：卷组：由一个或多个物理卷组成

LV：逻辑卷，LVM的逻辑卷类似于非LVM中的硬盘分区，LV就可以建立文件系统了，基于LV来建立文件系统文件系统，mkfs来格式化这个/dev/sda 最后变成一个个不同的文件系统

PE：每一个物理卷被划分为PE基本单元，是LVM最小的存储单元，具有唯一编号，PE大小可以手动制动，默认4MB

LE：逻辑卷也被划分成LE，可被寻址的基本单元，在同一个卷组中，PE和LE大小一定是相同的，而且要一一对应。 说白了就是把PE一个一个映射成LE

三、逻辑卷管理实验

3.1 普通逻辑卷创建

首先在服务器上添加一块硬盘

#查看磁盘信息[root@wentan ~]# lsblkNAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTsr0     11:0    1  6.6G  0 rom  nvme0n1259:0    0   25G  0 disk ├─nvme0n1p1   259:1    0    1G  0 part /boot└─nvme0n1p2   259:2    0   24G  0 part   ├─rhel-root 253:0    0   22G  0 lvm  /  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]nvme0n2259:3    0   20G  0 disk nvme0n3259:4    0   20G  0 disk #接下来把硬盘分区 分成一个5G大小的物理分区[root@wentan ~]# fdisk /dev/nvme0n2Welcome to fdisk (util-linux 2.32.1).Changes will remain in memory only, until you decide to write them.Be careful before using the write command.Device does not contain a recognized partition table.Created a new DOS disklabel with disk identifier 0x0230473b.Command (m for help): nPartition type   p   primary (0 primary, 0 extended, 4 free)   e   extended (container for logical partitions)Select (default p): pPartition number (1-4, default 1): 1First sector (2048-41943039, default 2048): Last sector, +sectors or +size{K,M,G,T,P} (2048-41943039, default 41943039): +5GCreated a new partition 1 of type 'Linux' and of size 5 GiB.Command (m for help): pDisk /dev/nvme0n2: 20 GiB, 21474836480 bytes, 41943040 sectorsUnits: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisklabel type: dosDisk identifier: 0x0230473bDevice  Boot Start      End  Sectors Size Id Type/dev/nvme0n2p12048 10487807 10485760   5G 83 LinuxCommand (m for help): wThe partition table has been altered.Calling ioctl() to re-read partition table.Syncing disks.#接下来查看分区结构[root@wentan ~]# lsblk NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTsr0     11:0    1  6.6G  0 rom  nvme0n1259:0    0   25G  0 disk ├─nvme0n1p1   259:1    0    1G  0 part /boot└─nvme0n1p2   259:2    0   24G  0 part   ├─rhel-root 253:0    0   22G  0 lvm  /  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]nvme0n2259:3    0   20G  0 disk └─nvme0n2p1   259:6    0    5G  0 part nvme0n3259:4    0   20G  0 disk#创建pv[root@wentan ~]# pvcreate /dev/nvme0n2p1   Physical volume "/dev/nvme0n2p1" successfully created.#查看详细信息[root@wentan ~]# pvdisplay /dev/nvme0n2p1   "/dev/nvme0n2p1" is a new physical volume of "5.00 GiB"  --- NEW Physical volume ---  PV Name /dev/nvme0n2p1  VG Name   PV Size 5.00 GiB  Allocatable    NO  PE Size 0     Total PE0  Free PE 0  Allocated PE   0  PV UUID 9lWVmv-IwRw-OgXz-2Jed-je5e-nKiA-fRS0C3#创建一个VG[root@wentan ~]# vgcreate -s 4M testvg /dev/nvme0n2p1   Volume group "testvg" successfully created[root@wentan ~]# vgdisplay testvg   --- Volume group ---  VG Name testvg  System ID Format  lvm2  Metadata Areas 1  Metadata Sequence No  1  VG Access      read/write  VG Status      resizable  MAX LV  0  Cur LV  0  Open LV 0  Max PV  0  Cur PV  1  Act PV  1  VG Size <5.00 GiB  PE Size 4.00 MiB  Total PE1279  Alloc PE / Size0 / 0     Free  PE / Size1279 / <5.00 GiB  VG UUID Ryu6s1-AglO-x4gY-UZL3-swFD-H07i-1Zw5Pb  #创建lv[root@wentan ~]# lvcreate -l 1024 -n testlv testvg  Logical volume "testlv" created.[root@wentan ~]# lvdisplay /dev/testvg/testlv   --- Logical volume ---  LV Path  /dev/testvg/testlv  LV Name  testlv  VG Name  testvg  LV UUID  dH7xlu-9cJa-eQ4P-Dui1-0RoL-02gY-lxeH1v  LV Write Access read/write  LV Creation host, time wentan, 2022-01-18 13:59:30 +0800  LV Statusavailable  # open   0  LV Size  4.00 GiB  Current LE      1024  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:2  # 创建文件系统[root@wentan ~]# mkfs.ext4 /dev/mapper/testvg-testlv mke2fs 1.44.3 (10-July-2018)Creating filesystem with 1048576 4k blocks and 262144 inodesFilesystem UUID: b8fe5156-37d8-4f31-9363-659d76ddd4daSuperblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736Allocating group tables: doneWriting inode tables: doneCreating journal (16384 blocks): doneWriting superblocks and filesystem accounting information: done #挂载[root@wentan ~]# mkdir /volume1[root@wentan ~]# vim /etc/fstab #外加一行/dev/mapper/testvg-testlv /volume1 ext4 defaults 0 0[root@wentan ~]# mount -a[root@wentan ~]# df -hTFilesystem  Type      Size  Used Avail Use% Mounted ondevtmpfs    devtmpfs  1.9G     0  1.9G   0% /devtmpfstmpfs     1.9G     0  1.9G   0% /dev/shmtmpfstmpfs     1.9G  9.7M  1.9G   1% /runtmpfstmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root     xfs 22G  4.2G   18G  19% //dev/nvme0n1p1     xfs      1014M  169M  846M  17% /boottmpfstmpfs     376M   16K  376M   1% /run/user/42tmpfstmpfs     376M  4.0K  376M   1% /run/user/0/dev/mapper/testvg-testlv ext4      3.9G   16M  3.7G   1% /volume1#看到最后这个逻辑卷挂载成功即实验完成

3.2 逻辑卷扩容

注意点 扩容大小限制是VG的大小限制，最多扩容不能超过VG的总大小

#扩容4.8G[root@wentan ~]# lvextend -L 4.8G /dev/testvg/testlv   Rounding size to boundary between physical extents: 4.80 GiB.  Size of logical volume testvg/testlv changed from 4.00 GiB (1024 extents) to 4.80 GiB (1229 extents).  Logical volume testvg/testlv successfully resized.  #刷新挂载点[root@wentan ~]# resize2fs /dev/testvg/testlv resize2fs 1.44.3 (10-July-2018)Filesystem at /dev/testvg/testlv is mounted on /volume1; on-line resizing requiredold_desc_blocks = 1, new_desc_blocks = 1The filesystem on /dev/testvg/testlv is now 1258496 (4k) blocks long.[root@wentan ~]# df -hTFilesystem  Type      Size  Used Avail Use% Mounted ondevtmpfs    devtmpfs  1.9G     0  1.9G   0% /devtmpfstmpfs     1.9G     0  1.9G   0% /dev/shmtmpfstmpfs     1.9G  9.7M  1.9G   1% /runtmpfstmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root     xfs 22G  4.2G   18G  19% //dev/nvme0n1p1     xfs      1014M  169M  846M  17% /boottmpfstmpfs     376M   16K  376M   1% /run/user/42tmpfstmpfs     376M  4.0K  376M   1% /run/user/0/dev/mapper/testvg-testlv ext4      4.7G   16M  4.4G   1% /volume1

注意

• 扩展文件系统xfs类型的文件系统用xfs_growfs /volume1，后面接的是挂载点的位置
• 如果是ext文件系统刷新要用resize2fs /dev/testvg/testlv 后面接的是逻辑卷的位置

3.3 swap分区的创建

注意： swap分区不需要通过LVM来管理，物理分区完成后，可以直接做成swap类型

[root@wentan /]# fdisk /dev/nvme0n2Welcome to fdisk (util-linux 2.32.1).Changes will remain in memory only, until you decide to write them.Be careful before using the write command.Command (m for help): nPartition type   p   primary (2 primary, 0 extended, 2 free)   e   extended (container for logical partitions)Select (default p): pPartition number (3,4, default 3): 3First sector (20973568-41943039, default 20973568): Last sector, +sectors or +size{K,M,G,T,P} (20973568-41943039, default 41943039): +2GCreated a new partition 3 of type 'Linux' and of size 2 GiB.Command (m for help): pDisk /dev/nvme0n2: 20 GiB, 21474836480 bytes, 41943040 sectorsUnits: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisklabel type: dosDisk identifier: 0x0230473bDevice  Boot    Start      End  Sectors Size Id Type/dev/nvme0n2p1   2048 10487807 10485760   5G 83 Linux/dev/nvme0n2p2      10487808 20973567 10485760   5G 83 Linux/dev/nvme0n2p3      20973568 25167871  4194304   2G 83 LinuxCommand (m for help): wThe partition table has been altered.Syncing disks.#直接做成swap[root@wentan ~]# mkswap /dev/nvme0n2p3 Setting up swapspace version 1, size = 2 GiB (2147479552 bytes)no label, UUID=47a1f300-73b6-464c-9d62-4f8527ff108e#查看UUID[root@wentan ~]# blkid /dev/nvme0n2p3/dev/nvme0n2p3: UUID="47a1f300-73b6-464c-9d62-4f8527ff108e" TYPE="swap" PARTUUID="0230473b-03"[root@wentan ~]# vim /etc/fstab/dev/nvme0n2p3 swap swap defaults 0 0#挂载所有swap[root@wentan ~]# swapon -a#查看所有swap[root@wentan ~]# swapon -sFilenameTypeSizeUsedPriority/dev/dm-1  partition21463000-2/dev/nvme0n2p3    partition20971480-3#查看系统所有swap总大小[root@wentan ~]# freetotal used free      shared  buff/cache   availableMem: 3848776      726408     257468010096      547688     2859772Swap:4243448    0     4243448

3.4 VDO卷的创建

什么是VDO技术，这是RHEL8中特有的技术

红帽公司收购了一个公司 叫 permabit ，VDO就是 permabit这个公司的技术

VDO也不是使用LVM来管理，是一个单独的技术。

VDO最大的作用就是节省硬盘空间，可以做到一个1TB的硬盘，直接存放3TB的数据甚至更多

VDO 是怎么实现这个功能的？

靠的就是删除和压缩解压缩技术 重删就是把硬盘里相同的数据以前要存多份，现在会把多余的删掉，只留一份。，压缩算法来节省空间。

我们要使用VDO技术 将一块20 GD的硬盘，直接做成60G，并且挂载到系统上直接使用

#安装两个软件#安装时间较长，大约需要几分钟，安装完成以后需要重启设备 [root@wentan ~]# yum install -y vdo kmod-kvdo[root@wentan ~]# reboot[root@wentan ~]# vdo create --name=testvdo --device=/dev/nvme0n3 --vdoLogicalSize=60GCreating VDO testvdo      The VDO volume can address 16 GB in 8 data slabs, each 2 GB.      It can grow to address at most 16 TB of physical storage in 8192 slabs.      If a larger maximum size might be needed, use bigger slabs.Starting VDO testvdoStarting compression on VDO testvdoVDO instance 0 volume is ready at /dev/mapper/testvdo[root@wentan ~]# lsblkNAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTsr0     11:0    1  6.6G  0 rom  nvme0n1259:0    0   25G  0 disk ├─nvme0n1p1   259:1    0    1G  0 part /boot└─nvme0n1p2   259:2    0   24G  0 part   ├─rhel-root 253:0    0   22G  0 lvm  /  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]nvme0n2259:3    0   20G  0 disk └─testvdo     253:2    0   60G  0 vdo  [root@wentan ~]# mkfs.xfs /dev/mapper/testvdo meta-data=/dev/mapper/testvdo    isize=512    agcount=4, agsize=3932160 blks  =  sectsz=4096  attr=2, projid32bit=1  =  crc=1 finobt=1, sparse=1, rmapbt=0  =  reflink=1data     =  bsize=4096   blocks=15728640, imaxpct=25  =  sunit=0      swidth=0 blksnaming   =version 2bsize=4096   ascii-ci=0, ftype=1log      =internal log    bsize=4096   blocks=7680, version=2  =  sectsz=4096  sunit=1 blks, lazy-count=1realtime =none     extsz=4096   blocks=0, rtextents=0[root@wentan ~]# mkdir /vdoblock[root@wentan ~]# vim /etc/fstab/dev/mapper/testvdo     /vdoblock xfs     defaults,x-systemd.requires=vdo.service 0 0[root@wentan ~]# mount -a[root@wentan ~]# df -hTFilesystem     Type      Size  Used Avail Use% Mounted ondevtmpfsdevtmpfs  1.8G     0  1.8G   0% /devtmpfs   tmpfs     1.9G     0  1.9G   0% /dev/shmtmpfs   tmpfs     1.9G  9.6M  1.9G   1% /runtmpfs   tmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root xfs 22G  4.5G   18G  21% //dev/nvme0n1p1 xfs      1014M  269M  746M  27% /boottmpfs   tmpfs     371M   16K  371M   1% /run/user/42tmpfs   tmpfs     371M  4.0K  371M   1% /run/user/0/dev/mapper/testvdo   xfs 60G  461M   60G   1% /vdoblock

3.5 逻辑卷的缩小

#查看一下目前的大小[root@wentan ~]# df -hTFilesystem  Type      Size  Used Avail Use% Mounted ondevtmpfs    devtmpfs  1.9G     0  1.9G   0% /devtmpfstmpfs     1.9G     0  1.9G   0% /dev/shmtmpfstmpfs     1.9G  9.7M  1.9G   1% /runtmpfstmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root     xfs 22G  4.2G   18G  19% //dev/nvme0n1p1     xfs      1014M  169M  846M  17% /boottmpfstmpfs     376M   16K  376M   1% /run/user/42/dev/mapper/testvg-testlv ext4      4.7G   16M  4.4G   1% /volume1tmpfstmpfs     376M  4.0K  376M   1% /run/user/0/dev/mapper/mvvg-mylv     xfs4.0G   61M  4.0G   2% /new-volume#在做磁盘裁剪的时候，首先必须要把文件系统给取消挂载[root@wentan ~]# umount /dev/mapper/testvg-testlv [root@wentan ~]# df -hTFilesystem     Type      Size  Used Avail Use% Mounted ondevtmpfsdevtmpfs  1.9G     0  1.9G   0% /devtmpfs   tmpfs     1.9G     0  1.9G   0% /dev/shmtmpfs   tmpfs     1.9G  9.7M  1.9G   1% /runtmpfs   tmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root xfs 22G  4.2G   18G  19% //dev/nvme0n1p1 xfs      1014M  169M  846M  17% /boottmpfs   tmpfs     376M   16K  376M   1% /run/user/42tmpfs   tmpfs     376M  4.0K  376M   1% /run/user/0/dev/mapper/mvvg-mylv xfs4.0G   61M  4.0G   2% /new-volume#裁剪前必须要检测文件系统，避免把文件系统的错误扩大化导致文件系统奔溃[root@wentan ~]# e2fsck -f /dev/testvg/testlv e2fsck 1.44.3 (10-July-2018)Pass 1: Checking inodes, blocks, and sizesPass 2: Checking directory structurePass 3: Checking directory connectivityPass 4: Checking reference countsPass 5: Checking group summary information/dev/testvg/testlv: 11/319488 files (0.0% non-contiguous), 40540/1258496 blocks[root@wentan ~]# resize2fs /dev/testvg/testlv 2Gresize2fs 1.44.3 (10-July-2018)Resizing the filesystem on /dev/testvg/testlv to 524288 (4k) blocks.The filesystem on /dev/testvg/testlv is now 524288 (4k) blocks long.[root@wentan ~]# lvreduce -L 2G /dev/testvg/testlv   WARNING: Reducing active logical volume to 2.00 GiB.  THIS MAY DESTROY YOUR DATA (filesystem etc.)Do you really want to reduce testvg/testlv? [y/n]: y  Size of logical volume testvg/testlv changed from 4.80 GiB (1229 extents) to 2.00 GiB (512 extents).  Logical volume testvg/testlv successfully resized.[root@wentan ~]# mount -a[root@wentan ~]# df -hTFilesystem  Type      Size  Used Avail Use% Mounted ondevtmpfs    devtmpfs  1.9G     0  1.9G   0% /devtmpfstmpfs     1.9G     0  1.9G   0% /dev/shmtmpfstmpfs     1.9G  9.7M  1.9G   1% /runtmpfstmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root     xfs 22G  4.2G   18G  19% //dev/nvme0n1p1     xfs      1014M  169M  846M  17% /boottmpfstmpfs     376M   16K  376M   1% /run/user/42tmpfstmpfs     376M  4.0K  376M   1% /run/user/0/dev/mapper/mvvg-mylv     xfs4.0G   61M  4.0G   2% /new-volume/dev/mapper/testvg-testlv ext4      2.0G   12M  1.8G   1% /volume1

3.6 逻辑卷的删除

[root@wentan ~]# umount /dev/mapper/testvg-testlv [root@wentan ~]# vim /etc/fstab #删除含有/dev/mapper/testvg-testlv的一行[root@wentan ~]# lvremove /dev/testvg/testlv Do you really want to remove active logical volume testvg/testlv? [y/n]: y  Logical volume "testlv" successfully removed[root@wentan ~]# vgremove testvg   Volume group "testvg" successfully removed[root@wentan ~]# pvremove /dev/nvme0n2p1  Labels on physical volume "/dev/nvme0n2p1" successfully wiped.[root@wentan ~]# df -hTFilesystem     Type      Size  Used Avail Use% Mounted ondevtmpfsdevtmpfs  1.9G     0  1.9G   0% /devtmpfs   tmpfs     1.9G     0  1.9G   0% /dev/shmtmpfs   tmpfs     1.9G  9.7M  1.9G   1% /runtmpfs   tmpfs     1.9G     0  1.9G   0% /sys/fs/cgroup/dev/mapper/rhel-root xfs 22G  4.2G   18G  19% //dev/nvme0n1p1 xfs      1014M  169M  846M  17% /boottmpfs   tmpfs     376M   16K  376M   1% /run/user/42tmpfs   tmpfs     376M  4.0K  376M   1% /run/user/0/dev/mapper/mvvg-mylv xfs4.0G   61M  4.0G   2% /new-volume

3.7 逻辑卷快照技术

LVM还具备有“快照卷”功能，该功能类似于虚拟机软件的还原时间点功能。例如，可以对某一个逻辑卷设备做一次快照，如果日后发现数据被改错了，就可以利用之前做好的快照卷进行覆盖还原。LVM的快照卷功能有两个特点：

• 快照卷的容量必须等同于逻辑卷的容量；

• 快照卷仅一次有效，一旦执行还原操作后则会被立即自动删除。

[root@wentan ~]# vgdisplay   --- Volume group ---  VG Name mvvg  System ID Format  lvm2  Metadata Areas 1  Metadata Sequence No  3  VG Access      read/write  VG Status      resizable  MAX LV  0  Cur LV  1  Open LV 1  Max PV  0  Cur PV  1  Act PV  1  VG Size <5.00 GiB  PE Size 4.00 MiB  Total PE1279  Alloc PE / Size1024 / 4.00 GiB  Free  PE / Size255 / 1020.00 MiB  VG UUID peXZzy-ldiM-hwer-d9Ih-Yfu4-F7dT-hWP1FB     --- Volume group ---  VG Name rhel  System ID Format  lvm2  Metadata Areas 1  Metadata Sequence No  3  VG Access      read/write  VG Status      resizable  MAX LV  0  Cur LV  2  Open LV 2  Max PV  0  Cur PV  1  Act PV  1  VG Size <24.00 GiB  PE Size 4.00 MiB  Total PE6143  Alloc PE / Size6143 / <24.00 GiB  Free  PE / Size0 / 0     VG UUID tLKo9C-urRn-PQ4C-lFCK-NnxX-5uSF-g7oknF#在还原时间点快照前写入一个文件，验证恢复快照不会丢失之前的文件 [root@wentan ~]# echo "hello,world" > /new-volume/readme.txt#检查刚刚写入的文件是否存在[root@wentan ~]# ls -l /new-volume/total 4-rw-r--r--. 1 root root 12 Jan 18 19:37 readme.txt#给这个lv卷打一个快照[root@wentan ~]# lvcreate -L 120M -s -n SNAP /dev/mvvg/mylv  Logical volume "SNAP" created.#查看lv所有卷组，会发现快照卷已经存在了[root@wentan ~]# lvdisplay   --- Logical volume ---  LV Path  /dev/mvvg/mylv  LV Name  mylv  VG Name  mvvg  LV UUID  mJoWZN-8lfH-lWTd-KEHZ-6eBs-bzl8-BAT8iw  LV Write Access read/write  LV Creation host, time wentan, 2022-01-18 19:23:25 +0800  LV snapshot status     source of    SNAP [active]  LV Statusavailable  # open   1  LV Size  4.00 GiB  Current LE      1024  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:3     --- Logical volume ---  LV Path  /dev/mvvg/SNAP  LV Name  SNAP  VG Name  mvvg  LV UUID  ZuO0eN-rEkX-9iYR-iDUu-Jrt2-w2wV-dE74rV  LV Write Access read/write  LV Creation host, time wentan, 2022-01-18 19:38:00 +0800  LV snapshot status     active destination for mylv  LV Statusavailable  # open   0  LV Size  4.00 GiB  Current LE      1024  COW-table size  120.00 MiB  COW-table LE    30  Allocated to snapshot  0.02%  Snapshot chunk size    4.00 KiB  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     256  Block device    253:5     --- Logical volume ---  LV Path  /dev/rhel/swap  LV Name  swap  VG Name  rhel  LV UUID  88Em5N-b1ye-gxHz-cPZN-eY0O-1RR7-2ZI1A2  LV Write Access read/write  LV Creation host, time localhost, 2022-01-05 04:16:15 +0800  LV Statusavailable  # open   2  LV Size  <2.05 GiB  Current LE      524  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:1     --- Logical volume ---  LV Path  /dev/rhel/root  LV Name  root  VG Name  rhel  LV UUID  wGxFLg-lFhu-cNG4-4TeI-DRxn-AnLu-HhfBQf  LV Write Access read/write  LV Creation host, time localhost, 2022-01-05 04:16:15 +0800  LV Statusavailable  # open   1  LV Size  <21.95 GiB  Current LE      5619  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:0  #在逻辑卷所挂载的目录中创建一个100MB的垃圾文件，然后再查看快照卷的状态。可以发现存储空间占的用量上升了[root@wentan ~]# dd if=/dev/zero of=/new-volume/files count=1 bs=100M1+0 records in1+0 records out104857600 bytes (105 MB, 100 MiB) copied, 0.751014 s, 140 MB/s[root@wentan ~]# lvdisplay   --- Logical volume ---  LV Path  /dev/mvvg/mylv  LV Name  mylv  VG Name  mvvg  LV UUID  mJoWZN-8lfH-lWTd-KEHZ-6eBs-bzl8-BAT8iw  LV Write Access read/write  LV Creation host, time wentan, 2022-01-18 19:23:25 +0800  LV snapshot status     source of    SNAP [active]  LV Statusavailable  # open   1  LV Size  4.00 GiB  Current LE      1024  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:3     --- Logical volume ---  LV Path  /dev/mvvg/SNAP  LV Name  SNAP  VG Name  mvvg  LV UUID  ZuO0eN-rEkX-9iYR-iDUu-Jrt2-w2wV-dE74rV  LV Write Access read/write  LV Creation host, time wentan, 2022-01-18 19:38:00 +0800  LV snapshot status     active destination for mylv  LV Statusavailable  # open   0  LV Size  4.00 GiB  Current LE      1024  COW-table size  120.00 MiB  COW-table LE    30  Allocated to snapshot  83.68%  Snapshot chunk size    4.00 KiB  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     256  Block device    253:5     --- Logical volume ---  LV Path  /dev/rhel/swap  LV Name  swap  VG Name  rhel  LV UUID  88Em5N-b1ye-gxHz-cPZN-eY0O-1RR7-2ZI1A2  LV Write Access read/write  LV Creation host, time localhost, 2022-01-05 04:16:15 +0800  LV Statusavailable  # open   2  LV Size  <2.05 GiB  Current LE      524  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:1     --- Logical volume ---  LV Path  /dev/rhel/root  LV Name  root  VG Name  rhel  LV UUID  wGxFLg-lFhu-cNG4-4TeI-DRxn-AnLu-HhfBQf  LV Write Access read/write  LV Creation host, time localhost, 2022-01-05 04:16:15 +0800  LV Statusavailable  # open   1  LV Size  <21.95 GiB  Current LE      5619  Segments 1  Allocation      inherit  Read ahead sectors     auto  - currently set to     8192  Block device    253:0  #恢复快照之前必须要取消挂载[root@rhel8-server /]# umount   /new-volume#通过lvconvert --merge 来指定快照SNAP恢复[root@wentan ~]# lvconvert --merge /dev/mvvg/SNAP   Merging of volume mvvg/SNAP started.  mvvg/mylv: Merged: 28.05%  mvvg/mylv: Merged: 100.00% #挂载所有卷组[root@wentan ~]# mount -a[root@wentan ~]# cd /new-volume/#此时刚刚的100M垃圾随着快照技术已经删除了[root@wentan new-volume]# lltotal 4-rw-r--r--. 1 root root 12 Jan 18 19:37 readme.txt

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