Disk management - logical volumes

introduce

Introduction to logical volumes

Logical volume manager is a mechanism used by Linux system to manage hard disk partitions
The original intention is to solve the defect that the hard disk device is not easy to modify the partition size after creating the partition. Although it is theoretically feasible to forcibly expand or shrink the traditional hard disk partition, it may cause data loss.
An abstraction layer based on physical storage devices, which has the advantage of flexible management
characteristic:
- Dynamic online capacity expansion (key)
- Offline clipping
- Data striping
- data mirroring

working principle

Physical Volume: Physical Volume (PV), which is at the bottom of LVM, can be understood as physical hard disk, hard disk partition or RAID disk array
Volume group: Volume Group (VG) is based on physical volumes. A volume group can contain multiple physical volumes, and new physical volumes can be added to the volume group after it is created. An LVM system can have only one volume group or multiple volume groups
Logical Volume: Logical Volume (LV). The Logical Volume is built on the volume group, and the Logical Volume can dynamically expand or reduce the space after it is built. It is a logical device used by the end user
Physical area: physical extent (PE). A physical volume can be divided into multiple PES. PE with unique number is the smallest unit that can be addressed by LVM. The size of PE can be specified, and the default is 4 MB. Once the PE size is determined, it cannot be changed. The PE size of all physical volumes in the same volume group is the same.
Logical area: logical extent (LE). A logical volume can be divided into multiple les, which is also the smallest unit addressed by LVM. In the same volume group, the size of Le and PE are the same and correspond to each other one by one.

Logical volume management

Common commands

Functions / commands	Physical volume management	Volume group management	Logical volume management
scanning	pvscan	vgscan	lvscan
establish	pvcreate	vgcreate	lvcreate
display	pvs	vgs	lvs
Detailed display	pvdisplay	vgdisplay	lvdisplay
delete	pvremove	vgremove	lvremove
extend		vgextend	lvextend
narrow		vgreduce	lvreduce

Logical volume creation

Physical device - > physical volume (pv) - > volume group (vg) - > logical volume (lv) - > logical volume format - > mount

Physical device: hard disk partition
[root@server1 ~]# fdisk /dev/sdb
[root@server1 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk 
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part 
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0    5G  0 disk 
├─sdb1            8:17   0    1G  0 part 
└─sdb2            8:18   0    2G  0 part 
sr0              11:0    1  973M  0 rom 
[root@server1 ~]# partprobe /dev/sdb

Create physical volume
[root@server1 ~]# pvcreate /dev/sdb1 /dev/sdb2
  Physical volume "/dev/sdb1" successfully created.
  Physical volume "/dev/sdb2" successfully created.
[root@server1 ~]# pvs
  PV         VG     Fmt  Attr PSize   PFree
  /dev/sda2  centos lvm2 a--  <19.00g    0 
  /dev/sdb1         lvm2 ---    1.00g 1.00g
  /dev/sdb2         lvm2 ---    2.00g 2.00g
[root@server1 ~]# pvdisplay /dev/sdb*
  "/dev/sdb2" is a new physical volume of "2.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb2
  VG Name               
  PV Size               2.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               ogYeQh-kmXp-SguX-IE5I-VY1T-HFSE-mgVzh2
   
  "/dev/sdb1" is a new physical volume of "1.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name               
  PV Size               1.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               O0FhDl-4USu-DBGD-skhu-zFVA-rEiZ-JVC3T3

Create volume group
[root@server1 ~]# vgcreate vg01 /dev/sdb1 /dev/sdb2
  Volume group "vg01" successfully created
[root@server1 ~]# vgs
  VG     #PV #LV #SN Attr   VSize   VFree
  centos   1   2   0 wz--n- <19.00g    0 
  vg01     2   0   0 wz--n-   2.99g 2.99g

Create logical volume
[root@server1 ~]# lvcreate -n lv01 -L 2.5G vg01
 Option Description:
-n: Specifies the logical volume name
-L: Specify the logical volume size directly
-l: Indirectly specify the logical volume size (plus) PE number/Volume group free space( VFree)Percentage)
[root@server1 ~]# lvs
  LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root centos -wi-ao---- <17.00g                                                    
  swap centos -wi-ao----   2.00g                                                    
  lv01 vg01   -wi-a-----   2.50g 

View mapping relationships
[root@server1 ~]# ll /dev/vg01/lv01 
lrwxrwxrwx 1 root root 7 8 December 21:17 /dev/vg01/lv01 -> ../dm-2
[root@server1 ~]# ll /dev/mapper/vg01-lv01 
lrwxrwxrwx 1 root root 7 8 December 21:17 /dev/mapper/vg01-lv01 -> ../dm-2

format
[root@server1 ~]# mkfs.ext4 /dev/vg01/lv01 
[root@server1 ~]# blkid /dev/vg01/lv01
/dev/vg01/lv01: UUID="acc1fc83-a64c-4d60-9f32-955169625ac1" TYPE="ext4" 

mount 
[root@server1 ~]# mkdir /mnt/lv01
[root@server1 ~]# mount /dev/vg01/lv01 /mnt/lv01/
[root@server1 ~]# df -Th
 file system                type      Capacity used available used% Mount point
devtmpfs                devtmpfs  899M     0  899M    0% /dev
tmpfs                   tmpfs     910M     0  910M    0% /dev/shm
tmpfs                   tmpfs     910M  9.6M  901M    2% /run
tmpfs                   tmpfs     910M     0  910M    0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.9G   16G   11% /
/dev/sda1               xfs      1014M  194M  821M   20% /boot
tmpfs                   tmpfs     182M     0  182M    0% /run/user/0
/dev/mapper/vg01-lv01   ext4      2.4G  7.5M  2.3G    1% /mnt/lv01

Logical volume deletion

Uncoupling
[root@server1 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk 
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part 
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0    5G  0 disk 
├─sdb1            8:17   0    1G  0 part 
│ └─vg01-lv01   253:2    0  2.5G  0 lvm  /mnt/lv01
└─sdb2            8:18   0    2G  0 part 
  └─vg01-lv01   253:2    0  2.5G  0 lvm  /mnt/lv01
sr0              11:0    1  973M  0 rom  
[root@server1 ~]# umount /dev/vg01/lv01

Delete logical volume
[root@server1 ~]# lvremove /dev/vg01/lv01
Do you really want to remove active logical volume vg01/lv01? [y/n]: y
  Logical volume "lv01" successfully removed

Delete volume group
[root@server1 ~]# vgremove vg01
  Volume group "vg01" successfully removed  

Delete physical volume
[root@server1 ~]# pvremove /dev/sdb[12]
  Labels on physical volume "/dev/sdb1" successfully wiped.
  Labels on physical volume "/dev/sdb2" successfully wiped.
[root@server1 ~]# pvs
  PV         VG     Fmt  Attr PSize   PFree
  /dev/sda2  centos lvm2 a--  <19.00g    0 
[root@server1 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk 
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part 
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0    5G  0 disk 
├─sdb1            8:17   0    1G  0 part 
└─sdb2            8:18   0    2G  0 part 
sr0              11:0    1  973M  0 rom

Dynamic expansion of logical volume

Prepare 0.5G Logical volumes for
[root@server1 ~]# pvcreate /dev/sdb1
  Physical volume "/dev/sdb1" successfully created.
[root@server1 ~]# vgcreate vg01 /dev/sdb1
  Volume group "vg01" successfully created
[root@server1 ~]# lvcreate -n lv01 -L 0.5G vg01
  Logical volume "lv01" created.
[root@server1 ~]# ll /dev/vg01/lv01 
lrwxrwxrwx 1 root root 7 8 September 21-13:10 /dev/vg01/lv01 -> ../dm-2
[root@server1 ~]# ll /dev/mapper/vg01-lv01 
lrwxrwxrwx 1 root root 7 8 September 21-13:10 /dev/mapper/vg01-lv01 -> ../dm-2
[root@server1 ~]# mkfs.ext4 /dev/vg01/lv01
[root@server1 ~]# mount /dev/vg01/lv01 /mnt/lv01/
[root@server1 ~]# df -Th
 file system                type      Capacity used available used% Mount point
devtmpfs                devtmpfs  899M     0  899M    0% /dev
tmpfs                   tmpfs     910M     0  910M    0% /dev/shm
tmpfs                   tmpfs     910M  9.6M  901M    2% /run
tmpfs                   tmpfs     910M     0  910M    0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.9G   16G   11% /
/dev/sda1               xfs      1014M  194M  821M   20% /boot
tmpfs                   tmpfs     182M     0  182M    0% /run/user/0
/dev/mapper/vg01-lv01   ext4      488M  780K  452M    1% /mnt/lv01

see/mnt/lv01 Which volume group does it belong to
[root@server1 ~]# lvs
  LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root centos -wi-ao---- <17.00g                                                    
  swap centos -wi-ao----   2.00g                                                    
  lv01 vg01   -wi-ao---- 512.00m       

see vg01 Remaining space
[root@server1 ~]# vgs
  VG     #PV #LV #SN Attr   VSize    VFree  
  centos   1   2   0 wz--n-  <19.00g      0 
  vg01     1   1   0 wz--n- 1020.00m 508.00m
#Insufficient volume group space: expand the volume group first, and then the logical volume
#The volume group has enough space. Only the logical volume needs to be expanded

Capacity expansion volume group: directly add other physical volumes to the volume group (if there are no free physical volumes, you can create physical volumes through physical devices)
[root@server1 ~]# vgextend vg01 /dev/sdb2
  Physical volume "/dev/sdb2" successfully created.
  Volume group "vg01" successfully extended
[root@server1 ~]# vgs
  VG     #PV #LV #SN Attr   VSize   VFree
  centos   1   2   0 wz--n- <19.00g    0 
  vg01     2   1   0 wz--n-   2.99g 2.49g

Expanding logical volumes
[root@server1 ~]# lvextend /dev/vg01/lv01 -L +2G
  Size of logical volume vg01/lv01 changed from 512.00 MiB (128 extents) to 2.50 GiB (640 extents).
  Logical volume vg01/lv01 successfully resized.
[root@server1 ~]# df -Th
 file system                type      Capacity used available used% Mount point
devtmpfs                devtmpfs  899M     0  899M    0% /dev
tmpfs                   tmpfs     910M     0  910M    0% /dev/shm
tmpfs                   tmpfs     910M  9.6M  901M    2% /run
tmpfs                   tmpfs     910M     0  910M    0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.9G   16G   11% /
/dev/sda1               xfs      1014M  194M  821M   20% /boot
tmpfs                   tmpfs     182M     0  182M    0% /run/user/0
/dev/mapper/vg01-lv01   ext4      488M  780K  452M    1% /mnt/lv01

Synchronous file system
[root@server1 ~]# resize2fs /dev/vg01/lv01 
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/vg01/lv01 is mounted on /mnt/lv01; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/vg01/lv01 is now 655360 blocks long.
[root@server1 ~]# df -Th
 file system                type      Capacity used available used% Mount point
devtmpfs                devtmpfs  899M     0  899M    0% /dev
tmpfs                   tmpfs     910M     0  910M    0% /dev/shm
tmpfs                   tmpfs     910M  9.6M  901M    2% /run
tmpfs                   tmpfs     910M     0  910M    0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.9G   16G   11% /
/dev/sda1               xfs      1014M  194M  821M   20% /boot
tmpfs                   tmpfs     182M     0  182M    0% /run/user/0
/dev/mapper/vg01-lv01   ext4      2.5G  1.5M  2.4G    1% /mnt/lv01

Striping logical volumes

Striping: divide the data saved to the logical volume into n equal parts and write them to different physical volumes respectively, which can improve the data reading and writing efficiency; If any of the physical volumes involved fails, the data cannot be recovered.

Create partition
[root@server1 ~]# fdisk /dev/sdb
[root@server1 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk 
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part 
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0    5G  0 disk 
├─sdb1            8:17   0    2G  0 part 
└─sdb2            8:18   0    2G  0 part 
sr0              11:0    1  973M  0 rom  

Refresh partition table (unsuccessful, you can try to restart)
[root@server1 ~]# partprobe /dev/sdb

Create physical volume
[root@server1 ~]# pvcreate /dev/sdb[12]
  Physical volume "/dev/sdb1" successfully created.
  Physical volume "/dev/sdb2" successfully created.
[root@server1 ~]# pvs /dev/sdb[12]
  PV         VG Fmt  Attr PSize PFree
  /dev/sdb1     lvm2 ---  2.00g 2.00g
  /dev/sdb2     lvm2 ---  2.00g 2.00g

Create volume group
[root@server1 ~]# vgcreate vg01 /dev/sdb[12]
  Volume group "vg01" successfully created
[root@server1 ~]# vgs vg01
  VG   #PV #LV #SN Attr   VSize VFree
  vg01   2   0   0 wz--n- 3.99g 3.99g

Create logical volumes for striping
[root@server1 ~]# lvcreate -n lv01 -l 100%free vg01 -i 2 /dev/sdb[12]
  Using default stripesize 64.00 KiB.
  Logical volume "lv01" created.
Option Description:
-i: Specifies the number of stripes
[root@server1 ~]# pvs /dev/sdb[12]
  PV         VG   Fmt  Attr PSize  PFree
  /dev/sdb1  vg01 lvm2 a--  <2.00g    0 
  /dev/sdb2  vg01 lvm2 a--  <2.00g    0
  
format
[root@server1 ~]# mkfs.xfs /dev/vg01/lv01 
meta-data=/dev/vg01/lv01         isize=512    agcount=8, agsize=130800 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=1046400, imaxpct=25
         =                       sunit=16     swidth=32 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=16 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

mount 
[root@server1 ~]# mkdir /mnt/lv01
[root@server1 ~]# mount /dev/vg01/lv01 /mnt/lv01

test
#Copy session for monitoring
[root@server1 ~]# yum install -y sysstat.x86_64
[root@server1 ~]# iostat -m -d /dev/sdb[12] 3
 Option Description:
-d: View disk
-m: At what speed, M/s
 3: Every 3 s Display once 
[root@server1 ~]# dd if=/dev/zero of=/mnt/lv01/dd_file bs=1M count=1000

#Monitoring display
Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sdb1            181.33         0.00        11.29          0         33
sdb2            180.33         0.00        11.27          0         33

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sdb1            731.33         0.00        45.58          0        136
sdb2            729.33         0.00        45.58          0        136

Logical volume snapshot

The snapshot size is much smaller than the logical volume instance size, and the snapshot space also comes from the volume group. When the available space of the volume group is 0, the snapshot cannot be created

Environment: now it is planned to vg01-lv01 The logical volume takes a snapshot, but the free space of the volume group is 0, which is proposed to be used sdb3 Capacity expansion
[root@server1 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk 
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part 
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0    5G  0 disk 
├─sdb1            8:17   0    2G  0 part 
│ └─vg01-lv01   253:2    0    4G  0 lvm  /mnt/lv01
├─sdb2            8:18   0    2G  0 part 
│ └─vg01-lv01   253:2    0    4G  0 lvm  /mnt/lv01
└─sdb3            8:19   0 1023M  0 part 
sr0              11:0    1  973M  0 rom  

Create physical volume
[root@server1 ~]# pvcreate /dev/sdb3
  Physical volume "/dev/sdb3" successfully created.

sdb3 join vg01 Volume group
[root@server1 ~]# vgextend vg01 /dev/sdb3
  Volume group "vg01" successfully extended
[root@server1 ~]# dmsetup ls --tree
vg01-lv01 (253:2)
 ├─ (8:18)
 └─ (8:17)
centos-swap (253:1)
 └─ (8:2)
centos-root (253:0)
 └─ (8:2)

take snapshot 
[root@server1 ~]# lvcreate -n lv01_snap -L 50M -s /dev/vg01/lv01
  Logical volume "lv01_snap" created.
[root@server1 ~]# lvs
  LV        VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root      centos -wi-ao---- <17.00g                                                    
  swap      centos -wi-ao----   2.00g                                                    
  lv01      vg01   owi-aos---   3.99g                                                    
  lv01_snap vg01   swi-a-s---  50.00m      lv01   0.15 
[root@server1 ~]# dmsetup ls --tree
vg01-lv01_snap (253:5)
 ├─vg01-lv01_snap-cow (253:4) #Save the data before the original volume changes
 │  └─ (8:19)
 └─vg01-lv01-real (253:3) #Real logical volume (original volume)
    ├─ (8:18)
    └─ (8:17)
vg01-lv01 (253:2)
 └─vg01-lv01-real (253:3)
    ├─ (8:18)
    └─ (8:17)
centos-swap (253:1)
 └─ (8:2)
centos-root (253:0)
 └─ (8:2)

Snapshot auto expansion
[root@server1 ~]# vim /etc/lvm/lvm.conf 
snapshot_autoextend_threshold = 75#Snapshot space utilization (if the value is set to 100, automatic capacity expansion is turned off)
snapshot_autoextend_percent = 20 #The snapshot utilization rate meets the above requirements, and the capacity is automatically expanded by 20%

Snapshot backup is often used in production environment

Lock table – > create snapshot – > unlock – > mount snapshot – > back up to a specified place – > delete snapshot

Keywords: Linux Operation & Maintenance lvm

Added by holowugz on Wed, 01 Sep 2021 22:34:04 +0300

Programming VIP

Disk management - logical volumes

Disk management - logical volumes

introduce

Introduction to logical volumes

working principle

Logical volume management

Common commands

Logical volume creation

Logical volume deletion

Dynamic expansion of logical volume

Striping logical volumes

Logical volume snapshot

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