硬盘分好区或者部署为 RAID 磁盘阵列之后，再想修改硬盘分区大小就不 容易了
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。
让新添加的两块硬盘设备支持 LVM 技术
[root@Node1 ~]# ls /sys/class/scsi_host/ //确定主机总线SCSI总线号 host0 host1 host2 [root@Node1 ~]# echo "- - -" > /sys/class/scsi_host/host0/scan //重新扫描 SCSI总线添加磁盘 [root@Node1 ~]# echo "- - -" > /sys/class/scsi_host/host1/scan [root@Node1 ~]# echo "- - -" > /sys/class/scsi_host/host2/scan [root@Node1 ~]# fdisk -l | grep "^Disk /dev" //检查硬盘是否在线 Disk /dev/sda: 53.7 GB, 53687091200 bytes, 104857600 sectors Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors Disk /dev/sdc: 32.2 GB, 32212254720 bytes, 62914560 sectors
让新添加的两块硬盘设备支持 LVM 技术
[root@ccc ~]# pvcreate /dev/sdb /dev/sdc Physical volume "/dev/sdb" successfully created. Physical volume "/dev/sdc" successfully created. [root@ccc ~]# vgcreate storage /dev/sdb /dev/sdc #添加storage卷组
Volume group "storage" successfully created
[root@ccc ~]# vgdisplay #查看新添加的卷组情况 --- Volume group --- VG Name storage System ID Format lvm2 Metadata Areas 2 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 2 Act PV 2 VG Size 39.99 GiB PE Size 4.00 MiB Total PE 10238 Alloc PE / Size 0 / 0 Free PE / Size 10238 / 39.99 GiB VG UUID 5fmYm8-vgOw-BqWB-7KJA-VozO-CwSy-CV3aYe --- Volume group --- VG Name centos 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 <19.00 GiB PE Size 4.00 MiB Total PE 4863 Alloc PE / Size 4863 / <19.00 GiB Free PE / Size 0 / 0 VG UUID CVLGL0-AlCR-uXLk-EYy3-rmPB-GnQ0-KPWdwz
切割出一个约为 150MB 的逻辑卷设备
在对逻辑卷进行切割时有两种计量单位。第一种是以容 量为单位，所使用的参数为-L。例如，使用-L 150M 生成一个大小为 150MB 的逻辑卷。另外 一种是以基本单元的个数为单位，所使用的参数为-l。每个基本单元的大小默认为 4MB。例 如，使用-l 37 可以生成一个大小为 37×4MB=148MB 的逻辑卷
lvcreate -n vo -l 37 storage
lvdisplay
把生成好的逻辑卷进行格式化，然后挂载使用
mkfs.ext4 /dev/storage/vo
创建挂载目录，进行挂载
mkdir /linuxprobe mount /dev/storage/vo /linuxprobe
查看挂载状态，并写入到配置文件，使其永久生效
df -h echo "/dev/storage/vo /linuxprobe ext4 defaults 0 0" >> / etc/fstab
扩容逻辑卷
用户在使用存储设备时感 知不到设备底层的架构和布局，更不用关心底层是由多少块硬盘组成的，只要卷组中 有足够的资源，就可以一直为逻辑卷扩容。扩展前请一定要记得卸载设备和挂载点的 关联。
[root@ccc ~]# umount /linuxprobe #卸载设备 [root@ccc ~]# lvextend -L 290M /dev/storage/vo #扩容到290M Rounding size to boundary between physical extents: 292.00 MiB. Size of logical volume storage/vo changed from 148.00 MiB (37 extents) to 292.00 MiB (73 extents). Logical volume storage/vo successfully resized. [root@ccc ~]# e2fsck -f /dev/storage/vo #检查硬盘完整性 e2fsck 1.42.9 (28-Dec-2013) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/storage/vo: 11/38000 files (0.0% non-contiguous), 10453/151552 blocks [root@ccc ~]# resize2fs /dev/storage/vo #重置硬盘容量 resize2fs 1.42.9 (28-Dec-2013) Resizing the filesystem on /dev/storage/vo to 299008 (1k) blocks. The filesystem on /dev/storage/vo is now 299008 blocks long. [root@ccc ~]# mount -a #重新挂载 [root@ccc ~]# df -h #查看验证 Filesystem Size Used Avail Use% Mounted on devtmpfs 475M 0 475M 0% /dev tmpfs 487M 0 487M 0% /dev/shm tmpfs 487M 7.7M 479M 2% /run tmpfs 487M 0 487M 0% /sys/fs/cgroup /dev/mapper/centos-root 17G 3.8G 14G 23% / /dev/sda1 1014M 138M 877M 14% /boot tmpfs 98M 0 98M 0% /run/user/0 /dev/mapper/storage-vo 279M 2.1M 259M 1% /linuxprobe [root@ccc ~]#
缩小逻辑卷
相较于扩容逻辑卷，在对逻辑卷进行缩容操作时，其丢失数据的风险更大。所以在生产 环境中执行相应操作时，一定要提前备份好数据。另外 Linux 系统规定，在对 LVM 逻辑卷进 行缩容操作之前，要先检查文件系统的完整性（当然这也是为了保证我们的数据安全）。在执 行缩容操作前记得先把文件系统卸载掉。
[root@ccc ~]# umount /linuxprobe #卸载挂载点 [root@ccc ~]# e2fsck -f /dev/storage/vo #检查数据完整性 e2fsck 1.42.9 (28-Dec-2013) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/storage/vo: 11/74000 files (0.0% non-contiguous), 15507/299008 blocks [root@ccc ~]# resize2fs /dev/storage/vo 120M #缩容到12M resize2fs 1.42.9 (28-Dec-2013) Resizing the filesystem on /dev/storage/vo to 122880 (1k) blocks. The filesystem on /dev/storage/vo is now 122880 blocks long. [root@ccc ~]# lvreduce -L 120M /dev/storage/vo #重置逻辑卷容量 WARNING: Reducing active logical volume to 120.00 MiB. THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce storage/vo? [y/n]: y Size of logical volume storage/vo changed from 292.00 MiB (73 extents) to 120.00 MiB (30 extents). Logical volume storage/vo successfully resized. [root@ccc ~]# mount -a #重新挂载 [root@ccc ~]# df -h #验证 Filesystem Size Used Avail Use% Mounted on devtmpfs 475M 0 475M 0% /dev tmpfs 487M 0 487M 0% /dev/shm tmpfs 487M 7.7M 479M 2% /run tmpfs 487M 0 487M 0% /sys/fs/cgroup /dev/mapper/centos-root 17G 3.8G 14G 23% / /dev/sda1 1014M 138M 877M 14% /boot tmpfs 98M 0 98M 0% /run/user/0 /dev/mapper/storage-vo 113M 1.6M 103M 2% /linuxprobe [root@ccc ~]#
逻辑卷快照
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@ccc ~]# vgdisplay #查看逻辑卷信息 --- Volume group --- VG Name storage System ID Format lvm2 Metadata Areas 2 Metadata Sequence No 4 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 1 Max PV 0 Cur PV 2 Act PV 2 VG Size 39.99 GiB PE Size 4.00 MiB Total PE 10238 Alloc PE / Size 30 / 120.00 MiB #使用了120M逻辑卷 Free PE / Size 10208 / <39.88 GiB #剩余磁盘空间 VG UUID 5fmYm8-vgOw-BqWB-7KJA-VozO-CwSy-CV3aYe --- Volume group --- VG Name centos 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 <19.00 GiB PE Size 4.00 MiB Total PE 4863 Alloc PE / Size 4863 / <19.00 GiB Free PE / Size 0 / 0 VG UUID CVLGL0-AlCR-uXLk-EYy3-rmPB-GnQ0-KPWdwz [root@ccc ~]# clear [root@ccc ~]# echo "Welcome to Linuxprobe.com" > /linuxprobe/readme.txt #在逻辑卷挂载目录下创建一个文件 [root@ccc ~]# ls -l /linuxprobe/readme.txt -rw-r--r--. 1 root root 26 Sep 27 15:00 /linuxprobe/readme.txt [root@ccc ~]# ls -l /linuxprobe total 14 drwx------. 2 root root 12288 Sep 27 14:19 lost+found -rw-r--r--. 1 root root 26 Sep 27 15:00 readme.txt [root@ccc ~]# lvcreate -L 120M -s -n SNAP /dev/storage/vo #创建一个快照SNAP，大小120M,还需要在命 令后面写上是针对哪个逻辑卷执行的快照操作 Logical volume "SNAP" created. [root@ccc ~]# lvdisplay #查看 --- Logical volume --- LV Path /dev/storage/vo LV Name vo VG Name storage LV UUID X7HzFw-x1B6-st30-lcJt-Xuag-mSi1-R62cnm LV Write Access read/write LV Creation host, time ccc.liutao.com, 2021-09-27 14:08:15 +0800 LV snapshot status source of SNAP [active] #快照状态 LV Status available # open 1 LV Size 120.00 MiB #快照卷大小 Current LE 30 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:2 --- Logical volume --- LV Path /dev/storage/SNAP LV Name SNAP VG Name storage LV UUID Sn1FWG-FCLn-J97O-rU1w-1XHC-SGyG-HX51vf LV Write Access read/write LV Creation host, time ccc.liutao.com, 2021-09-27 15:01:44 +0800 LV snapshot status active destination for vo #vo逻辑卷的快照 LV Status available # open 0 LV Size 120.00 MiB Current LE 30 COW-table size 120.00 MiB COW-table LE 30 Allocated to snapshot 0.01% #占用情况 Snapshot chunk size 4.00 KiB Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:5 --- Logical volume --- LV Path /dev/centos/swap LV Name swap VG Name centos LV UUID Wpvm1Z-1ysn-T0B7-EeE8-qyTL-J33e-lCCYy7 LV Write Access read/write LV Creation host, time localhost, 2021-09-10 11:55:27 +0800 LV Status available # open 2 LV Size 2.00 GiB Current LE 512 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:1 --- Logical volume --- LV Path /dev/centos/root LV Name root VG Name centos LV UUID 1seXT8-3rrk-eFGz-iTcR-oXmq-1pE2-5pbewa LV Write Access read/write LV Creation host, time localhost, 2021-09-10 11:55:27 +0800 LV Status available # open 1 LV Size <17.00 GiB Current LE 4351 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:0 [root@ccc ~]# dd if=/dev/zero of=/linuxprobe/files count=1 bs=100M #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 1+0 records in 1+0 records out 104857600 bytes (105 MB) copied, 2.77815 s, 37.7 MB/s [root@ccc ~]# lvdisplay --- Logical volume --- LV Path /dev/storage/vo LV Name vo VG Name storage LV UUID X7HzFw-x1B6-st30-lcJt-Xuag-mSi1-R62cnm LV Write Access read/write LV Creation host, time ccc.liutao.com, 2021-09-27 14:08:15 +0800 LV snapshot status source of SNAP [active] LV Status available # open 1 LV Size 120.00 MiB Current LE 30 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:2 --- Logical volume --- LV Path /dev/storage/SNAP LV Name SNAP VG Name storage LV UUID Sn1FWG-FCLn-J97O-rU1w-1XHC-SGyG-HX51vf LV Write Access read/write LV Creation host, time ccc.liutao.com, 2021-09-27 15:01:44 +0800 LV snapshot status active destination for vo LV Status available # open 0 LV Size 120.00 MiB Current LE 30 COW-table size 120.00 MiB COW-table LE 30 Allocated to snapshot 76.91% #占用情况 Snapshot chunk size 4.00 KiB Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:5 --- Logical volume --- LV Path /dev/centos/swap LV Name swap VG Name centos LV UUID Wpvm1Z-1ysn-T0B7-EeE8-qyTL-J33e-lCCYy7 LV Write Access read/write LV Creation host, time localhost, 2021-09-10 11:55:27 +0800 LV Status available # open 2 LV Size 2.00 GiB Current LE 512 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:1 --- Logical volume --- LV Path /dev/centos/root LV Name root VG Name centos LV UUID 1seXT8-3rrk-eFGz-iTcR-oXmq-1pE2-5pbewa LV Write Access read/write LV Creation host, time localhost, 2021-09-10 11:55:27 +0800 LV Status available # open 1 LV Size <17.00 GiB Current LE 4351 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:0 [root@ccc ~]#
为了校验 SNAP 快照卷的效果，需要对逻辑卷进行快照还原操作。在此之前记 得先卸载掉逻辑卷设备与目录的挂载。
[root@ccc ~]# umount /linuxprobe/ [root@ccc ~]# lvconvert --merge /dev/storage/SNAP Merging of volume storage/SNAP started. storage/vo: Merged: 100.00% [root@ccc ~]# mount -a [root@ccc ~]# ls /linuxprobe/ lost+found readme.txt [root@ccc ~]# lvdisplay --- Logical volume --- LV Path /dev/storage/vo LV Name vo VG Name storage LV UUID X7HzFw-x1B6-st30-lcJt-Xuag-mSi1-R62cnm LV Write Access read/write LV Creation host, time ccc.liutao.com, 2021-09-27 14:08:15 +0800 LV Status available # open 1 LV Size 120.00 MiB Current LE 30 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:2 --- Logical volume --- LV Path /dev/centos/swap LV Name swap VG Name centos LV UUID Wpvm1Z-1ysn-T0B7-EeE8-qyTL-J33e-lCCYy7 LV Write Access read/write LV Creation host, time localhost, 2021-09-10 11:55:27 +0800 LV Status available # open 2 LV Size 2.00 GiB Current LE 512 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:1 --- Logical volume --- LV Path /dev/centos/root LV Name root VG Name centos LV UUID 1seXT8-3rrk-eFGz-iTcR-oXmq-1pE2-5pbewa LV Write Access read/write LV Creation host, time localhost, 2021-09-10 11:55:27 +0800 LV Status available # open 1 LV Size <17.00 GiB Current LE 4351 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:0
删除快照后，创建的100M垃圾也没有了
删除逻辑卷
当生产环境中想要重新部署 LVM 或者不再需要使用 LVM 时，则需要执行 LVM 的删除 操作。为此，需要提前备份好重要的数据信息，然后依次删除逻辑卷、卷组、物理卷设备，这 个顺序不可颠倒
取消逻辑卷与目录的挂载关联，删除配置文件中永久生效的设备参数 [root@ccc ~]# umount /linuxprobe/ [root@ccc ~]# vim /etc/fstab [root@ccc ~]# cat /etc/fstab # # /etc/fstab # Created by anaconda on Fri Sep 10 11:55:28 2021 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # /dev/mapper/centos-root / xfs defaults 0 0 UUID=feb40a38-e230-4cce-9038-2c53eaa707dc /boot xfs defaults 0 0 /dev/mapper/centos-swap swap swap defaults 0 0 #/dev/storage/vo /linuxprobe ext4 defaults 0 0 #删除永久生效设备参数 [root@ccc ~]# lvremove /dev/storage/vo #删除逻辑卷 Do you really want to remove active logical volume storage/vo? [y/n]: y Logical volume "vo" successfully removed [root@ccc ~]# vgremove storage #删除卷组 Volume group "storage" successfully removed [root@ccc ~]# pvremove /dev/sdb /dev/sdc #删除物理卷 Labels on physical volume "/dev/sdb" successfully wiped. Labels on physical volume "/dev/sdc" successfully wiped. [root@ccc ~]#
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