Linux下通过LVM对磁盘进行动态扩容 (Linux的逻辑卷)

1 LVM是什么

1.1 概念解释

LVM(Logical Volume Manager), 逻辑卷管理, 是一种将一至多个硬盘的分区在逻辑上进行组合, 当成一个大硬盘来使用。

当硬盘空间不足时, 可以动态地添加其它硬盘的分区到已有的卷组中 —— 磁盘空间的动态管理。

1.2 为什么用LVM

LVM通常用于装备大量磁盘的系统, 比如服务器中的磁盘阵列.

但LVM同样适用于仅有一、两块硬盘的小系统.

1.2.1 不使用LVM时的扩容思路

传统的文件系统是基于分区的, 一个文件系统对应一个分区, 这种方式比较直观, 但不易改变:

(1) 不同的分区相互独立, 单独的文件不能跨分区存储, 容易出现硬盘的利用率不均衡;

(2) 当一个文件系统/分区装满时, 是不能对其进行扩容的, 只能采用重新分区/建立文件系统, 重新分区会丢失数据, 就要:

① 做数据的迁移和备份;
② 或者把分区中的数据移到另一个更大的分区中;
③ 或者采用符号连接的方式使用其它分区的空间 —— 都非常麻烦;

(3) 如果要把硬盘上的多个分区合并在一起使用, 只能采用重新分区的方式, —— 需要做好数据的备份与恢复.

1.2.2 使用LVM时的扩容思路

使用LVM时技术时, 情况有所不同:

(1) 硬盘的多个分区由LVM统一管理为卷组, 可以很轻松地加入或移走某个分区 —— 也就是扩大或减小卷组的可用容量, 充分利用硬盘空间;

(2) 文件系统建立在逻辑卷上, 而逻辑卷可以根据需要改变大小(在卷组容量范围内)以满足要求;

(3) 文件系统建立在LVM上, 可以跨分区存储访问, 更加方便;

强烈建议对拥有多个磁盘的系统, 使用LVM管理磁盘.

1.3 名词解释

PV(Physical Volume): 物理卷, 处于LVM最底层, 可以是物理硬盘或者分区;

PP(Physical Extend): 物理区域, PV中可以用于分配的最小存储单元, 可以在创建PV的时候指定, 如1M, 2M, 4M, 8M…..组成同一VG中所有PV的PE大小应该相同;

VG(Volume Group): 卷组, 建立在PV之上, 可以含有一个到多个PV;

LV(Logical Volume): 逻辑卷, 建立在VG之上, 相当于原来分区的概念, 不过大小可以动态改变.

2 普通的挂载磁盘方法

2.1 创建分区的主要操作

(1) 查看分区情况 – fdisk -l

[root@localhost ~]# fdisk -l    Disk /dev/sda: 299.0 GB, 298999349248 bytes         # 磁盘/dev/sda  255 heads, 63 sectors/track, 36351 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x4d69fe0e       Device Boot      Start         End      Blocks   Id  System  /dev/sda1   *           1          26      204800   83  Linux       # 分为2个区, sda1  Partition 1 does not end on cylinder boundary.  /dev/sda2              26       36352   291785728   8e  Linux LVM   # sda2    # 磁盘/dev/sdb没有分区  Disk /dev/sdb: 4000.0 GB, 3999999721472 bytes  255 heads, 63 sectors/track, 486305 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x00000000    ......

(2) 查看已有磁盘 – lsblk

[root@localhost ~]# lsblk   NAME                       MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT  sda                          8:0    0 278.5G  0 disk   ├─sda1                       8:1    0   200M  0 part /boot  └─sda2                       8:2    0 278.3G  0 part     └─VolGroup-LogVol (dm-0) 253:0    0   1.9T  0 lvm  /      # LVM类型的分区  sdb                          8:32   0   3.7T  0 disk        # 还没有分区的新磁盘

(3) 对新磁盘进行分区 – fdisk /dev/sdb

[root@localhost ~]# fdisk /dev/sdb   Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel  Building a new DOS disklabel with disk identifier 0xf91f8c4c.  Changes will remain in memory only, until you decide to write them.  After that, of course, the previous content won't be recoverable.    Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)    WARNING: The size of this disk is 4.0 TB (4000225165312 bytes).  DOS partition table format can not be used on drives for volumes  larger than (2199023255040 bytes) for 512-byte sectors. Use parted(1) and GUID   partition table format (GPT).      WARNING: DOS-compatible mode is deprecated. It's strongly recommended to           switch off the mode (command 'c') and change display units to           sectors (command 'u').    Command (m for help): n             # n 表示新建分区  Command action     e   extended     p   primary partition (1-4)  p                                   # p 表示分区类型为主分区, 主分区只有1-4种选择  Partition number (1-4): 1           # 主分区的编号  First cylinder (1-486333, default 1):   # 开始扇区号, 直接回车, 使用默认值1  Using default value 1    # 结束扇区号, 使用默认值 --- 这里只加载了新磁盘的一半(2T), 所以还需要再次创建分区/dev/sdb2使用剩下的一半.  Last cylinder, +cylinders or +size{K,M,G} (1-267349, default 267349):     Using default value 267349    Command (m for help):  w            #  将上述设置写入分区表并退出  The partition table has been altered!    Calling ioctl() to re-read partition table.  Syncing disks.

(4) 再次查看分区情况 – fdisk -l

多出来一个/dev/sdb1的区, 这个1就是之前主分区之后指定的分区编号.

[root@localhost ~]# fdisk -l     Disk /dev/sda: 299.0 GB, 298999349248 bytes  255 heads, 63 sectors/track, 36351 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x4d69fe0e       Device Boot      Start         End      Blocks   Id  System  /dev/sda1   *           1          26      204800   83  Linux  Partition 1 does not end on cylinder boundary.  /dev/sda2              26       36352   291785728   8e  Linux LVM    # /dev/sdb磁盘:   Disk /dev/sdb: 4000.0 GB, 3999999721472 bytes  255 heads, 63 sectors/track, 486305 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x8f3043b5    # 多出来的分区/dev/sdb1     Device Boot      Start         End      Blocks   Id  System  /dev/sdb1               1      267349  2147480811   83  Linux    ......

(5) 查看当前分区表中的分区信息 – cat /proc/partitions

[root@localhost ~]# cat /proc/partitions   major minor  #blocks  name       8        0   291991552  sda     8        1      204800  sda1     8        2   291785728  sda2     8       32  3906249728  sdb      # 添加的新磁盘     8       33  2147480811  sdb1     # 创建的新分区   253        0  2046660608  dm-0

如果创建完之后,cat /proc/partitions 查看不到对应的分区, 使用 parprobe 刷新命令即可:

[root@localhost ~]# partprobe /dev/sdc

2.2 格式化新分区

(1) 格式化新分区 – mkfs -t

这里建议将新分区格式化为ext4文件类型, 还有ext2, ext3等文件类型, 区别请参考博客 ext2、ext3与ext4的区别 .

[root@localhost ~]# mkfs -t ext4 /dev/sdb1  mke2fs 1.41.12 (17-May-2010)  Filesystem label=  OS type: Linux  Block size=4096 (log=2)  Fragment size=4096 (log=2)  Stride=0 blocks, Stripe width=0 blocks  134217728 inodes, 536870202 blocks  26843510 blocks (5.00%) reserved for the super user  First data block=0  Maximum filesystem blocks=4294967296  16384 block groups  32768 blocks per group, 32768 fragments per group  8192 inodes per group  Superblock backups stored on blocks:           32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,           4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,           102400000, 214990848, 512000000    Writing inode tables:  8874/16384

(2) 等待一小会后, 将出现下述提示, 说明格式化完成:

Writing inode tables: done                              Creating journal (32768 blocks): done  Writing superblocks and filesystem accounting information:  done    This filesystem will be automatically checked every 26 mounts or  180 days, whichever comes first.  Use tune2fs -c or -i to override.

2.3 挂载新分区

(1) 创建目录, 并将 /dev/sdb1挂在到该目录下:

[root@localhost /]# mkdir data && cd /data  [root@localhost data]# mount /dev/sdc1 /data1

(2) 查看挂载是否成功:

[root@localhost data]# df -l  Filesystem                   1K-blocks       Used  Available Use% Mounted on  /dev/mapper/VolGroup-LogVol  286901696   18601728  253726196   7% /  tmpfs                         66020980          0   66020980   0% /dev/shm  /dev/sda1                       495844      33476     436768   8% /boot    # 挂载成功:   /dev/sdb1                   2113784984     202776 2006208168   1% /data

2.4 设置开机自动挂载

编辑文件 /etc/fstab:

[root@localhost data]# vim /etc/fstab    # 文件内容如下:   # /etc/fstab  # Created by anaconda on Wed Sep 12 10:41:40 2018  #  # 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/VolGroup-LogVol  /                     ext4    defaults        1 1  /dev/sdb1                    /data                 ext4    defaults        1 1  UUID=22b1d425-d050-43c3-a735-06d48bbb9051 /boot    ext4    defaults        1 2   tmpfs                        /dev/shm              tmpfs   defaults        0 0  devpts                       /dev/pts              devpts  gid=5,mode=620  0 0  sysfs                        /sys                  sysfs   defaults        0 0  proc                         /proc                 proc    defaults        0 0

3 LVM方式挂载磁盘 – 推荐

3.1 查看磁盘容量信息

[root@localhost ~]# df -h  Filesystem               Size  Used  Avail  Use%  Mounted on  /dev/mapper/VG-LogVol    1.9T  1.8T    61G   97%  /          # LVM卷组-逻辑卷  tmpfs                     63G     0    63G    0%  /dev/shm  /dev/sda1                485M   40M   421M    9%  /boot

3.2 查看磁盘扇区信息

[root@localhost ~]# fdisk -l    Disk /dev/sda: 299.0 GB, 298999349248 bytes         # 磁盘/dev/sda  255 heads, 63 sectors/track, 36351 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x4d69fe0e       Device Boot      Start         End      Blocks   Id  System  /dev/sda1   *           1          26      204800   83  Linux       # 分为2个区, sda1  Partition 1 does not end on cylinder boundary.  /dev/sda2              26       36352   291785728   8e  Linux LVM   # LVM类型的sda2    # 新添加的磁盘/dev/sdb, 没有分区  Disk /dev/sdb: 4000.0 GB, 3999999721472 bytes  255 heads, 63 sectors/track, 486305 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x00000000    # LVM格式的卷组信息:   Disk /dev/mapper/VolGroup-LogVol: 4294 MB, 4294967296 bytes  255 heads, 63 sectors/track, 522 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x00000000

3.3 创建分区

[root@localhost ~]# fdisk /dev/sdb  Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel  Building a new DOS disklabel with disk identifier 0x5b3d66ba.  Changes will remain in memory only, until you decide to write them.  After that, of course, the previous content won't be recoverable.    Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)    WARNING: The size of this disk is 4.0 TB (3999999721472 bytes).  DOS partition table format can not be used on drives for volumes  larger than (2199023255040 bytes) for 512-byte sectors. Use parted(1) and GUID   partition table format (GPT).      WARNING: DOS-compatible mode is deprecated. It's strongly recommended to           switch off the mode (command 'c') and change display units to           sectors (command 'u').    Command (m for help): n         # 添加分区  Command action     e   extended     p   primary partition (1-4)  p                               # 添加主分区  Partition number (1-4): 1       # 1号主分区, 即/dev/sdb1  First cylinder (1-486305, default 1):                 Using default value 1  Last cylinder, +cylinders or +size{K,M,G} (1-267349, default 267349): 486305  Value out of range.  Last cylinder, +cylinders or +size{K,M,G} (1-267349, default 267349):   Using default value 267349    Command (m for help): n         # 继续添加分区  Command action     e   extended     p   primary partition (1-4)  p  Partition number (1-4): 2       # 2号主分区, 即/dev/sdc2  First cylinder (267350-486305, default 267350):   Using default value 267350  Last cylinder, +cylinders or +size{K,M,G} (267350-486305, default 486305):   Using default value 486305    Command (m for help): p         # 打印分区信息:     Disk /dev/sdb: 4000.0 GB, 3999999721472 bytes  255 heads, 63 sectors/track, 486305 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x5b3d66ba       Device Boot      Start         End      Blocks   Id  System  /dev/sdb1               1      267349  2147480811   83  Linux  /dev/sdb2          267350      486305  1758764070   83  Linux    Command (m for help): t         # 转换类型  Partition number (1-4): 1  Partition number (1-4): 1           # 修改/dev/sdb1为Linux LVM类型:   Hex code (type L to list codes): L  # 查看可用类型:      0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris           1  FAT12           39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-   2  XENIX root      3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-   3  XENIX usr       40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-   4  FAT16 <32M      41  PPC PReP Boot   85  Linux extended  c7  Syrinx            5  Extended        42  SFS             86  NTFS volume set da  Non-FS data       6  FAT16           4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .   7  HPFS/NTFS       4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility      8  AIX             4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt            9  AIX bootable    50  OnTrack DM      93  Amoeba          e1  DOS access        a  OS/2 Boot Manag 51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O           b  W95 FAT32       52  CP/M            9f  BSD/OS          e4  SpeedStor         c  W95 FAT32 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs           e  W95 FAT16 (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  GPT               f  W95 Ext'd (LBA) 55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/  10  OPUS            56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b  11  Hidden FAT12    5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor        12  Compaq diagnost 61  SpeedStor       a9  NetBSD          f4  SpeedStor        14  Hidden FAT16 <3 63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary    16  Hidden FAT16    64  Novell Netware  af  HFS / HFS+      fb  VMware VMFS      17  Hidden HPFS/NTF 65  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE   18  AST SmartSleep  70  DiskSecure Mult b8  BSDI swap       fd  Linux raid auto  1b  Hidden W95 FAT3 75  PC/IX           bb  Boot Wizard hid fe  LANstep          1c  Hidden W95 FAT3 80  Old Minix       be  Solaris boot    ff  BBT              1e  Hidden W95 FAT1  Hex code (type L to list codes): 8e     # 修改为8e, 即Linux LVM类型  Changed system type of partition 1 to 8e (Linux LVM)    Command (m for help): t  Partition number (1-4): 2               # 修改/dev/sdc2为Linux LVM类型  Hex code (type L to list codes): 8e  Changed system type of partition 2 to 8e (Linux LVM)    Command (m for help): p                 # 再次查看相关信息:     Disk /dev/sdc: 4000.0 GB, 3999999721472 bytes  255 heads, 63 sectors/track, 486305 cylinders  Units = cylinders of 16065 * 512 = 8225280 bytes  Sector size (logical/physical): 512 bytes / 512 bytes  I/O size (minimum/optimal): 512 bytes / 512 bytes  Disk identifier: 0x5b3d66ba       Device Boot      Start         End      Blocks   Id  System  /dev/sdb1               1      267349  2147480811   8e  Linux LVM   # Id已改变  /dev/sdb2          267350      486305  1758764070   8e  Linux LVM    Command (m for help): w                 # 保存并退出  The partition table has been altered!   # 修改成功    Calling ioctl() to re-read partition table.  Syncing disks.

3.4 创建物理卷

[root@localhost ~]# pvcreate /dev/sdb1    Physical volume "/dev/sdb1" successfully created  [root@localhost ~]# pvcreate /dev/sdb2    Physical volume "/dev/sdb2" successfully created

3.5 扩展卷组

# 查看已有卷组, 发现该卷组就是需要扩容的卷组, 就不必再次创建卷组, 而是直接扩展卷组即可:   [root@localhost ~]# vgs    VG       #PV #LV #SN Attr   VSize VFree    VolGroup   2   2   0 wz--n- 1.91t    0     # 扩展卷组:   [root@localhost ~]# vgextend VolGroup /dev/sdb1    Volume group "VolGroup" successfully extended  [root@localhost ~]# vgextend VolGroup /dev/sdb2    Volume group "VolGroup" successfully extended

说明: 如果出现下述无法挂载物理磁盘到卷组中的信息, 说明这块物理磁盘已经挂载了, 需要先卸载, 然后再执行创建分区+卷组的操作:

[root@localhost /]# vgextend VolGroup /dev/sdb1     No physical volume label read from /dev/sdb1    Physical volume /dev/sdb1 not found    Can't open /dev/sdb1 exclusively.  Mounted filesystem?    Unable to add physical volume '/dev/sdb1' to volume group 'VolGroup'.

3.6 扩展逻辑卷

# 扩展逻辑卷, 即扩容:   [root@localhost ~]# lvextend -l +100%FREE /dev/mapper/VolGroup-LogVol     Extending logical volume lv_root to 5.54 TiB    Logical volume lv_root successfully resized    # 上述命令是将所有的空闲空间都扩容到逻辑卷中, 也可指定扩容的大小:   lvextend -l +100G /dev/mapper/VolGroup-LogVol 

3.7 查看磁盘卷组信息

[root@localhost ~]# lsblk   NAME                        MAJ:MIN RM   SIZE RO  TYPE  MOUNTPOINT  sda                           8:0    0 278.5G  0  disk    ├─sda1                        8:1    0   500M  0  part  /boot  └─sda2                        8:2    0   278G  0  part      ├─VolGroup-LogVol (dm-0)  253:0    0   5.6T  0  lvm   /  sdb                           8:16   0   1.6T  0  disk    └─sdb1                        8:17   0   1.6T  0  part      └─VolGroup-LogVol (dm-0)  253:0    0   5.6T  0  lvm   /  sdc                           8:32   0   3.7T  0  disk    ├─sdc1                        8:33   0     2T  0  part    │ └─VolGroup-LogVol (dm-0)  253:0    0   5.6T  0  lvm   /  └─sdc2                        8:34   0   1.7T  0  part      └─VolGroup-LogVol (dm-0)  253:0    0   5.6T  0  lvm   /

3.8 调整文件系统的大小

# CentOS 7重新读取磁盘大小:   [root@localhost ~]# xfs_growfs /dev/mapper/VolGroup-LogVol   xfs_growfs: /dev/mapper/VolGroup-LogVol is not a mounted XFS filesystem    # CentOS 6.5重新读取磁盘大小:   # ext4格式, resize2fs会遍历整个磁盘, 速度比较慢, 但是不影响读写数据, 可以令其在后台运行.   [root@localhost ~]# resize2fs /dev/mapper/VolGroup-LogVol   resize2fs 1.41.12 (17-May-2010)  Filesystem at /dev/mapper/VolGroup-LogVol is mounted on /; on-line resizing required  old desc_blocks = 122, new_desc_blocks = 355  Performing an on-line resize of /dev/mapper/VolGroup-lv_root to 1487098880 (4k) blocks.    # 等了差不多20分钟, 出来了下面这货:    The filesystem on /dev/mapper/VolGroup-LogVol is now 1487098880 blocks long.     # 赶紧看下扩容成果吧:   [root@localhost ~]#   df -h  Filesystem                    Size  Used Avail Use%  Mounted on  /dev/mapper/VolGroup-LogVol   5.5T  1.8T  3.5T  34%  /          # 扩容成功  tmpfs                          63G     0   63G   0%  /dev/shm  /dev/sda1                     485M   40M  421M   9%  /boot

3.9 附录 – 创建卷组

对应 [3.5] 节的扩展卷组, 如果卷组不存在, 则需要创建之. 下述VolGroup是卷组名称.

vgcreate VolGroup /dev/sdb1  # 创建逻辑卷, 名称为: mylv. (操作系统中将产生: /dev/VolGroup/mylv目录)  # 将当前卷组中的100G空间分配到逻辑卷中  lvcreate -L 100G VolGroup -n mylv  # 或将当前卷组中的所有空闲空间全都分配到逻辑卷中:    lvcreate -l +100%FREE VolGroup -n mylv    # 格式化逻辑卷组:   mkfs -t ext4 /dev/VolGroup/mylv    # 挂载卷组到指定目录下, 如果是挂载到根目录, 则无需向/etc/fstab文件中添加启动项.   mount -t ext4 /dev/VolGroup/mylv /data

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