Create an LV - Best Practices| Alibaba Cloud Documentation Center

Background information

Logical Volume Manager (LVM) is a disk partition management mechanism for Linux ECS instances and features dynamic management of hard disks. In this mechanism, a logical layer is created on hard disks and partitions to help you manage hard disks and partitions in a more flexible manner. You can dynamically adjust the LV size without losing existing data. The existing LV remains unchanged even if you add new data disks.

Notice A snapshot backs up only the data of a single cloud disk. When LVM is used, data differences may occur when you roll back cloud disks.

Step 1: Create a PV

Remotely connect to an ECS instance as a root user. For more information, see Overview.

Run the following command to view information about all cloud disks on the ECS instance:

lsblk

If the following information is displayed, you can use five cloud disks to create a resizable LV by using LVM.

root@lvs06:~# lsblk
NAME   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda    252:0040G  0 disk
└─vda1 252:1040G  0 part /
vdb    252:1601T  0 disk
vdc    252:3201T  0 disk
vdd    252:4801T  0 disk
vde    252:6401T  0 disk
vdf    252:8001T  0 disk

Run the following command to create a physical volume (PV):

pvcreate <Device name of data disk 1> ... <Device name of data disk N>

If you want to add multiple data disks, you can add multiple device names. Separate multiple names with spaces.

root@lvs06:~# pvcreate /dev/vdb /dev/vdc /dev/vdd /dev/vde /dev/vdf
  Physical volume "/dev/vdb" successfully created.
  Physical volume "/dev/vdc" successfully created.
  Physical volume "/dev/vdd" successfully created.
  Physical volume "/dev/vde" successfully created.
  Physical volume "/dev/vdf" successfully created.

Run the following command to view information about the created PV on the ECS instance:

lvmdiskscan

A command output similar to the following one is displayed:

root@lvs06:~# lvmdiskscan | grep LVM
  /dev/vdb  [       1.00 TiB] LVM physical volume
  /dev/vdc  [       1.00 TiB] LVM physical volume
  /dev/vdd  [       1.00 TiB] LVM physical volume
  /dev/vde  [       1.00 TiB] LVM physical volume
  /dev/vdf  [       1.00 TiB] LVM physical volume
  5 LVM physical volume whole disks
  0 LVM physical volumes

Step 2: Create a VG

Run the following command to create a volume group (VG):
```
vgcreate <VG name> <Name of PV 1> ...... <Name of PV N>
```
If you want to add multiple PVs, you can add multiple PV names. Separate multiple names with spaces. You can customize the VG name. Example: lvm_01.
```
root@lvs06:~# vgcreate lvm_01 /dev/vdb /dev/vdc /dev/vdd /dev/vde /dev/vdf
  Volume group "lvm_01" successfully created
```

Run the following command to add a PV to the VG:

vgextend VG name  <Name of PV 1> ...... <Name of PV N>

The following command output shows that a PV is added to the lvm_01 VG:

root@lvs06:~# vgextend lvm_01 /dev/vdb /dev/vdc /dev/vdd /dev/vde /dev/vdf
  Volume group "lvm_01" successfully extended

Run the following command to view the VG information:
```
vgs
```
A command output similar to the following one is displayed:
```
root@lvs06:~# vgs
  VG     #PV #LV #SN Attr   VSize  VFree
  lvm_01   600 wz--n- <6.00t <6.00t
```

Step 3: Create an LV

Run the following command to create an LV:
```
lvcreate [-L <LV size>][ -n <LV name>] <VG name>
```
Note
- LV size: The LV size must be smaller than the free space of the VG. The unit can be MiB, GiB, or TiB.
- LV name: You can customize the name.
- VG name: the name of an existing VG.
The following command output shows that a 5 TiB LV is created:
```
root@lvs06:~# lvcreate -L 5T -n lv01 lvm_01
  Logical volume "lv01" created.
```

Run the following command to view the LV details:

lvdisplay

A command output similar to the following one is displayed:

root@lvs06:~# lvdisplay
  --- Logical volume ---
  LV Path                /dev/lvm_01/lv01
  LV Name                lv01
  VG Name                lvm_01
  LV UUID                svB00x-l6Ke-ES6M-ctsE-9P6d-dVj2-o0h***
  LV Write Access        read/write
  LV Creation host, time lvs06, 2019-06-0615:27:19 +0800
  LV Status              available
  # open                 0
  LV Size                5.00 TiB
  Current LE             1310720
  Segments               6
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

Step 4: Create and mount a file system

Run the following command to create a file system on the LV:

mkfs. <File system format> <LV path>

The following command output shows that an ext4 file system is created:

root@lvs06:~# mkfs.ext4 /dev/lvm_01/lv01
mke2fs 1.44.1 (24-Mar-2018)
Creating filesystem with13421772804k blocks and 167772160 inodes
Filesystem UUID: 2529002f-9209-4b6a-9501-106c1145c***
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
        102400000, 214990848, 512000000, 550731776, 644972544

Allocating group tables: done
Writing inode tables: done
Creating journal (262144 blocks): done
Writing superblocks and filesystem accounting information:
done

Create a mount point. Example: /media/lv01.
You can also use an existing mount point.
```
mkdir /media/lv01
```
Run the following command to mount the file system:
In this example, the LV path is /dev/lvm_01/lv01, and the mount point is /media /lv01. You can modify the LV path and mount point based on your actual needs.
```
mount /dev/lvm_01/lv01 /media/lv01
```

Run the following command to check whether the file system is mounted on the LV:

df -h

A command output similar to the following one is displayed:

root@lvs06:~# df -h
Filesystem               Size  Used Avail Use% Mounted on
udev                      12G     012G   0% /dev
tmpfs                    2.4G  3.7M  2.4G   1% /run
/dev/vda1                 40G  3.6G   34G  10% /
tmpfs                     12G     0   12G   0% /dev/shm
tmpfs                    5.0M     05.0M   0% /run/lock
tmpfs                     12G     012G   0% /sys/fs/cgroup
tmpfs                    2.4G     02.4G   0% /run/user/0
/dev/mapper/lvm_01-lv01  5.0T   89M  4.8T   1% /media/lv01

Prerequisites

Background information

Step 1: Create a PV

Step 2: Create a VG

Step 3: Create an LV

Step 4: Create and mount a file system