Centos7中磁盘管理及扩展

前提要求：

虚拟机：centos7 虚拟机软件：VMware Workstation 12

在安装Centos系统时，磁盘选择为LVM逻辑卷。当选择为LVM后才能创建逻辑卷等（必须）

数据格式选择的是xfs，很多讲解使用的是ext3，但以后xfs的优势会比ext越来越大。（可选）

参考原博主文章：https://blog.csdn.net/geoffreychan/article/details/77418111

LVM是Logical Volume Manager（逻辑卷管理）的简写，它是Linux环境下对硬盘分区进行管理的一种机制。LVM是建立在硬盘和分区上的逻辑层，它允许跨硬盘、分区创建逻辑卷并创建文件系统，可以很方便执行增加、扩展、删除等操作。

1、物理卷

物理卷（Physical Volume,PV）：就是指硬盘分区，也可以是整个硬盘或已创建的软RAID，是LVM的基本存储设备。在创建逻辑卷之前需要先创建物理卷，然后将多个物理卷组合创建卷组，最后在卷组的基础上创建逻辑卷。

可以将空白硬盘或分区加入主机，系统识别到新的硬盘sdb后，使用pvcreate对硬盘创建PV。

添加新硬盘或直接扩展分区的方式：直接扩展/或直接新添加一个硬盘

代码实现：

[root@Centos7T ~]#lsblk /dev/sdb    #你新建的分区可能存在该分区下
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb    8:16   0  20G  0 disk
[root@Centos7T ~]#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.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x6200a0ac.
Command (m for help): p   #查看信息

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: 0x6200a0ac

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    20973567    10485760   83  Linux
Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 8e           # 修改系统ID为 Linux LVM
Changed type of partition 'Linux' to 'Linux LVM'

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: 0x6200a0ac

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    20973567    10485760   8e  Linux LVM

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

Calling ioctl() to re-read partition table.
Syncing disks.

#先重启机器再执下一句，否则会找不到新建的磁盘
[root@Centos7T ~]#pvcreate /dev/sdb1        # 创建物理卷
WARNING: xfs signature detected on /dev/sdb1 at offset 0. Wipe it? [y/n]: y
  Wiping xfs signature on /dev/sdb1.
  Physical volume "/dev/sdb1" successfully created.
[root@Centos7T ~]#pvdisplay
  "/dev/sdb1" is a new physical volume of "10.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name               
  PV Size               10.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               xT6409-MGxH-M7Dy-TvZz-Fl55-qarO-Bb1n3U

在上面的代码中Hex code (type L to list all codes): 8e指定分区的系统ID为Linux LVM。空白为分区磁盘直接使用pvcreate /dev/sdb命令，系统ID自动转成Linux LVM。

2、卷组

卷组（Volume Group,VG）：是由一个或多个物理卷所组成的存储池，在卷组上能创建一个或多个逻辑卷。现在使用vgcreate命令对上文创建的PV（单个物理卷）创建卷组。 
代码实现：

[root@Centos7T ~]#vgcreate -s 10M vg0 /dev/sdb1     # 创建卷组vg0,指定物理块PE大小10M,并将pv:/dev/sdb1加入vg0.
  Volume group "vg0" successfully created
[root@Centos7T ~]#vgdisplay             # 查看所有卷组的信息.后面接具体卷组名,可查看指定卷组信息
  --- Volume group ---
  VG Name               vg0
  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               9.99 GiB
  PE Size               10.00 MiB
  Total PE              1023
  Alloc PE / Size       0 / 0   
  Free  PE / Size       1023 / 9.99 GiB
  VG UUID               46Z4tB-d71l-nfir-t6sB-cZPo-SBfl-eFCDIj
[root@Centos7T ~]#pvdisplay          # 查看所当前物理卷的信息.后面可接具体物理卷设备,可查看指定物理卷信息
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               vg0              # 已加入卷组vg0
  PV Size               10.00 GiB / not usable 10.00 MiB
  Allocatable           yes
  PE Size               10.00 MiB        # pe大小
  Total PE              1023             # 当前物理卷的pe总数
  Free PE               1023             # 当前物理卷的未被划分逻辑卷的pe总数
  Allocated PE          0
  PV UUID               xT6409-MGxH-M7Dy-TvZz-Fl55-qarO-Bb1n3U

3、创建逻辑卷

逻辑卷（Logical Volume,LV）：类似于非LVM系统中的硬盘分区，它建立在卷组之上，是一个标准的块设备，在逻辑卷之上可以建立文件系统。可以使用lvcreate命令创建逻辑卷 
代码实现：

[root@Centos7T ~]#lvcreate -n lv0 -l 100%vg vg0     # 使用vg0的全部空间创建逻辑卷lv0
  Logical volume "lv0" created.
[root@Centos7T ~]#lvdisplay
  --- Logical volume ---
  LV Path                /dev/vg0/lv0
  LV Name                lv0
  VG Name                vg0
  LV UUID                zGNz6W-N4QC-m3ZF-ey3h-mP7i-gFJ3-DjGMX1
  LV Write Access        read/write
  LV Creation host, time Centos7.magedu.com, 2017-08-19 21:27:34 +0800
  LV Status              available
  # open                 0
  LV Size                9.99 GiB
  Current LE             1023
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

[root@Centos7T ~]#pvdisplay
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               vg0
  PV Size               10.00 GiB / not usable 10.00 MiB
  Allocatable           yes (but full)
  PE Size               10.00 MiB
  Total PE              1023
  Free PE               0
  Allocated PE          1023
  PV UUID               xT6409-MGxH-M7Dy-TvZz-Fl55-qarO-Bb1n3U

[root@Centos7T ~]#lsblk -f /dev/sdb
NAME        FSTYPE      LABEL UUID                                   MOUNTPOINT
sdb                                                                  
└─sdb1      LVM2_member       xT6409-MGxH-M7Dy-TvZz-Fl55-qarO-Bb1n3U
  └─vg0-lv0

会在/dev下生成一个新的设备文件：

[root@Centos7T ~]#ll /dev/vg0/lv0
lrwxrwxrwx. 1 root root 7 Aug 19 21:27 /dev/vg0/lv0 -> ../dm-0     # 软链接文件
[root@Centos7T ~]#ll /dev/dm-0
brw-rw----. 1 root disk 253, 0 Aug 19 21:27 /dev/dm-0

4、文件系统

在逻辑卷lv0创建完成后话需要创建文件系统并挂载到制定目录才能够使用,当然还需要将挂载信息写入/etc/fstab文件 
代码实现：

[root@Centos7T ~]#mkfs.xfs /dev/vg0/lv0           # 创建文件系统
meta-data=/dev/vg0/lv0           isize=512    agcount=4, agsize=654720 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=2618880, 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@Centos7T ~]#lsblk /dev/sdb -f
NAME        FSTYPE      LABEL UUID                                   MOUNTPOINT
sdb                                                                  
└─sdb1      LVM2_member       xT6409-MGxH-M7Dy-TvZz-Fl55-qarO-Bb1n3U
  └─vg0-lv0 xfs               549cfbaa-a6dc-4161-a765-5f55af78131a   
[root@Centos7T ~]#lsblk /dev/vg0/lv0 -f
NAME    FSTYPE LABEL UUID                                 MOUNTPOINT
vg0-lv0 xfs          549cfbaa-a6dc-4161-a765-5f55af78131a
[root@Centos7T ~]#mkdir /mnt/lv0 && mount /dev/vg0/lv0 /mnt/lv0     # 将逻辑卷挂载到制定目录
[root@Centos7T ~]#df -T             # 查看挂载点
Filesystem          Type     1K-blocks    Used Available Use% Mounted on
/dev/sda2           xfs       52403200 4605416  47797784   9% /
/dev/sda1           xfs        1038336  172116    866220  17% /boot
/dev/sda5           xfs       52403200  376288  52026912   1% /app
/dev/sr0            iso9660    8086368 8086368         0 100% /run/media/root/CentOS 7 x86_64
/dev/mapper/vg0-lv0 xfs       10465280   32944  10432336   1% /mnt/lv0
[root@Centos7T ~]#blkid /dev/vg0/lv0
/dev/vg0/lv0: UUID="549cfbaa-a6dc-4161-a765-5f55af78131a" TYPE="xfs"
[root@Centos7T ~]#df -T /dev/vg0/lv0
Filesystem          Type 1K-blocks  Used Available Use% Mounted on
/dev/mapper/vg0-lv0 xfs   10465280 32944  10432336   1% /mnt/lv0
[root@Centos7T ~]#echo "UUID=549cfbaa-a6dc-4161-a765-5f55af78131a /mnt/lv0                 xfs    defaults        0 0" >> /etc/fstab
[root@Centos7T ~]#cat /etc/fstab | egrep "UUID"
UUID=806ef114-dff2-4c17-aff7-c95bc67faf40 /                       xfs     defaults        0 0
UUID=3df87bb6-2f6f-4d3f-af94-5ec47d2a9796 /app                    xfs     defaults        0 0
UUID=1e7ba91a-85c8-442b-b105-bc61c00ddbee /boot                   xfs     defaults        0 0
UUID=cc0e9678-d369-4bb9-9039-fd2f322df8b4 swap                    swap    defaults        0 0
UUID=549cfbaa-a6dc-4161-a765-5f55af78131a /mnt/lv0                 xfs    defaults        0 0

5、扩展逻辑卷

我们可以很方便的多逻辑卷进行扩展，不论是使用新的空白磁盘还是已有的空白分区。其大致实现原理为：对空白分区创建物理卷，然后将物理卷加入到需要扩展逻辑卷所在的卷组，最后扩大逻辑卷空间。如果逻辑卷所在的卷组还有空闲的空间（PE）可被使用且足够大，则甚至不需要另外的分区或者磁盘。

代码实现： 
修改系统ID并创建PV

[root@Centos7T ~]#lsblk -f /dev/sdc
NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
sdc                                                      
└─sdc1 xfs          6ef26358-ce07-4b0c-b28b-07caa90838bd
[root@Centos7T ~]#fdisk /dev/sdc
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/sdc: 32.2 GB, 32212254720 bytes, 62914560 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: 0xe20e9d16

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048    62914559    31456256   83  Linux

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): p

Disk /dev/sdc: 32.2 GB, 32212254720 bytes, 62914560 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: 0xe20e9d16

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048    62914559    31456256   8e  Linux LVM

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

Calling ioctl() to re-read partition table.
Syncing disks.
[root@Centos7T ~]#pvcreate /dev/sdc1          # 在指定分区上创建物理卷
WARNING: xfs signature detected on /dev/sdc1 at offset 0. Wipe it? [y/n]: y
  Wiping xfs signature on /dev/sdc1.
  Physical volume "/dev/sdc1" successfully created.
[root@Centos7T ~]#pvs
  PV         VG  Fmt  Attr PSize  PFree
  /dev/sdb1  vg0 lvm2 a--   9.99g     0
  /dev/sdc1      lvm2 ---  30.00g 30.00g

将PV加入到指定VG

[root@Centos7T ~]#vgextend vg0 /dev/sdc1          # 将物理卷加入已有的卷组
  Volume group "vg0" successfully extended
[root@Centos7T ~]#vgs
  VG  #PV #LV #SN Attr   VSize  VFree
  vg0   2   1   0 wz--n- 39.98g 29.99g            # VFREE为30G，即为新增物理卷的空间
[root@Centos7T ~]#pvdisplay /dev/sdc1
  --- Physical volume ---
  PV Name               /dev/sdc1
  VG Name               vg0
  PV Size               30.00 GiB / not usable 9.00 MiB
  Allocatable           yes
  PE Size               10.00 MiB
  Total PE              3071
  Free PE               3071
  Allocated PE          0
  PV UUID               Ez6ZFl-xjWR-gQHp-O3Yj-vTza-2OCE-h7Jccy

可知，将新建的PV加入到vg0后，vg0也有了30G的可用空间。同时/dev/sdc1的PE大小自动与/dev/sdb1同步为10M。 
扩展逻辑卷LV

[root@Centos7T ~]#lvs
  LV   VG  Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv0  vg0 -wi-ao---- 9.99g                                                    

[root@Centos7T ~]#lvextend -l 100%free /dev/vg0/lv0      # 扩展逻辑卷，使用卷组的全部可用空间
  Size of logical volume vg0/lv0 changed from 9.99 GiB (1023 extents) to 29.99 GiB (3071 extents).
  Logical volume vg0/lv0 successfully resized.
[root@Centos7T ~]#lvs
  LV   VG  Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv0  vg0 -wi-ao---- 29.99g                                       
[root@Centos7T ~]#lvdisplay
  --- Logical volume ---
  LV Path                /dev/vg0/lv0
  LV Name                lv0
  VG Name                vg0
  LV UUID                zGNz6W-N4QC-m3ZF-ey3h-mP7i-gFJ3-DjGMX1
  LV Write Access        read/write
  LV Creation host, time Centos7.magedu.com, 2017-08-19 21:27:34 +0800
  LV Status              available
  # open                 1
  LV Size                29.99 GiB
  Current LE             3071
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

[root@Centos7T ~]#xfs_growfs /dev/vg0/lv0   #如果为xfs需要用这种方式写入系统才能生效
[root@Centos7T ~]#lsblk -f /dev/sd{b,c}
NAME        FSTYPE      LABEL UUID                                   MOUNTPOINT
sdb                                                                  
└─sdb1      LVM2_member       xT6409-MGxH-M7Dy-TvZz-Fl55-qarO-Bb1n3U
  └─vg0-lv0 xfs               549cfbaa-a6dc-4161-a765-5f55af78131a   /mnt/lv0
sdc                                                                  
└─sdc1      LVM2_member       Ez6ZFl-xjWR-gQHp-O3Yj-vTza-2OCE-h7Jccy
  └─vg0-lv0 xfs               549cfbaa-a6dc-4161-a765-5f55af78131a   /mnt/lv0

5 删除逻辑卷

本文由于更多是演示，删除逻辑卷会卷组、物理卷一并彻底删除。但实际生产中可能只是单独删除逻辑卷，卷组、物理卷还会保留。当然，实际生产中很少需要删除逻辑卷。在删除逻辑卷之前，所有有用的资料都需要备份转移。 
代码实现：

[root@Centos7T ~]#sed -i '/lv0/d' /etc/fstab && umount /mnt/lv0/      # 删除配置信息
[root@Centos7T ~]#cat /etc/fstab | egrep "UUID"
UUID=806ef114-dff2-4c17-aff7-c95bc67faf40 /                       xfs     defaults        0 0
UUID=3df87bb6-2f6f-4d3f-af94-5ec47d2a9796 /app                    xfs     defaults        0 0
UUID=1e7ba91a-85c8-442b-b105-bc61c00ddbee /boot                   xfs     defaults        0 0
UUID=cc0e9678-d369-4bb9-9039-fd2f322df8b4 swap                    swap    defaults        0 0
[root@Centos7T ~]#df -T
Filesystem     Type     1K-blocks    Used Available Use% Mounted on
/dev/sda2      xfs       52403200 4605388  47797812   9% /
/dev/sda1      xfs        1038336  172116    866220  17% /boot
/dev/sda5      xfs       52403200  376288  52026912   1% /app
/dev/sr0       iso9660    8086368 8086368         0 100% /run/media/root/CentOS 7 x86_64
[root@Centos7T ~]#lvs
  LV   VG  Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv0  vg0 -wi-a----- 29.99g
[root@Centos7T ~]#lvremove /dev/vg0/lv0         # 移除逻辑卷
Do you really want to remove active logical volume vg0/lv0? [y/n]: y
  Logical volume "lv0" successfully removed
[root@Centos7T ~]#lvs
[root@Centos7T ~]#vgs
  VG  #PV #LV #SN Attr   VSize  VFree
  vg0   2   0   0 wz--n- 39.98g 39.98g
[root@Centos7T ~]#vgremove vg0                  # # 移除卷组
  Volume group "vg0" successfully removed
[root@Centos7T ~]#vgs
[root@Centos7T ~]#pvs
  PV         VG Fmt  Attr PSize  PFree
  /dev/sdb1     lvm2 ---  10.00g 10.00g
  /dev/sdc1     lvm2 ---  30.00g 30.00g
[root@Centos7T ~]#pvremove /dev/sdb1 /dev/sdc1      # 移除物理卷
  Labels on physical volume "/dev/sdb1" successfully wiped.
  Labels on physical volume "/dev/sdc1" successfully wiped.
[root@Centos7T ~]#pvs
[root@Centos7T ~]#lsblk -f /dev/sd{b,c}
NAME   FSTYPE      LABEL UUID                                   MOUNTPOINT
sdb                                                             
└─sdb1                                                          
sdc                                                             
└─sdc1 LVM2_member       Ez6ZFl-xjWR-gQHp-O3Yj-vTza-2OCE-h7Jccy

至此，逻辑卷删除完成。当然，/dev/sdc1显示LVM2_member（实际上sdb1也是的），这是由于我们前面将/dev/sdc1的系统ID改为8e导致的，重新将系统ID改回83即可。