Creating a Logical Volume Using LVM

Scenarios

This section shows how to create a 15 GB logical volume based on two 10 GB EVS disks.

Logical volumes can be created based on EVS disks with different specifications.

The process includes creating physical volumes, create a volume group, and create a logical volume.

Figure 1 Process of creating an LVM logical volume

Prerequisites

Two EVS disks have been attached to the ECS where LVM is installed.

Procedure

1. Log in to the ECS as user root.
2. Run the following command to view and take note of the device names:

   fdisk -l | grep /dev/vd | grep -v vda

   Information similar to the following is displayed:

   [root@ecs-lvmtest ~]# fdisk -l | grep /dev/vd | grep -v vda
   Disk /dev/vdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
   Disk /dev/vdc: 10.7 GB, 10737418240 bytes, 20971520 sectors

   In the command output, two EVS disks are attached to the ECS, and the device names are /dev/vdb and /dev/vdc.

3. Create physical volumes using EVS disks.
   1. Run the following command to create physical volumes using EVS disks:

      pvcreate Device name 1 Device name 2 Device name 3...

      Parameter description:

      Device name: indicates the disk device name. If multiple physical volumes need to be created in a batch, specify multiple device names and separate them with spaces.

      In this example, run the following command:

      pvcreate /dev/vdb /dev/vdc

      Information similar to the following is displayed:

      [root@ecs-lvmtest ~]#  pvcreate /dev/vdb /dev/vdc
        Physical volume "/dev/vdb" successfully created.
        Physical volume "/dev/vdc" successfully created.

   2. Run the following command to query details of the physical volumes:

      pvdisplay

      Information similar to the following is displayed:

      [root@ecs-lvmtest ~]# pvdisplay
        "/dev/vdc" is a new physical volume of "10.00 GiB"
        --- NEW Physical volume ---
        PV Name               /dev/vdc
        VG Name
        PV Size               10.00 GiB
        Allocatable           NO
        PE Size               0
        Total PE              0
        Free PE               0
        Allocated PE          0
        PV UUID               dypyLh-xjIj-PvG3-jD0j-yup5-O7SI-462R7C
      
        "/dev/vdb" is a new physical volume of "10.00 GiB"
        --- NEW Physical volume ---
        PV Name               /dev/vdb
        VG Name
        PV Size               10.00 GiB
        Allocatable           NO
        PE Size               0
        Total PE              0
        Free PE               0
        Allocated PE          0
        PV UUID               srv5H1-tgLu-GRTl-Vns8-GfNK-jtHk-Ag4HHB

      In the command output, the system has two new physical volumes named /dev/vdc and /dev/vdb.

4. Create a volume group for the physical volumes.
   1. Run the following command to create a volume group:

      vgcreate Volume group name Physical volume name 1 Physical volume name 2 Physical volume name 3...

      Parameter description:

      • Volume group name: Specify a volume group name, for example, vgdata.
      • Physical volume name: Specify the name of a physical volume to be added to the volume group. Multiple names are separated with spaces.

      In this example, run the following command:

      vgcreate vgdata /dev/vdb /dev/vdc

      Information similar to the following is displayed:

      [root@ecs-lvmtest ~]# vgcreate vgdata /dev/vdb /dev/vdc
        Volume group "vgdata" successfully created

   2. Run the following command to query details of the volume group:

      vgdisplay

      Information similar to the following is displayed:

      [root@ecs-lvmtest ~]# vgdisplay
        --- Volume group ---
        VG Name               vgdata
        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               19.99 GiB
        PE Size               4.00 MiB
        Total PE              5118
        Alloc PE / Size       0 / 0
        Free  PE / Size       5118 / 19.99 GiB
        VG UUID               NLkZV7-hYYE-0w66-tnlt-Y6jL-Ik7S-76w4P6

5. Create a logical volume in the volume group.
   1. Run the following command to create a logical volume:

      lvcreate -L Logical volume size -n Logical volume name Volume group name

      Parameter description:

      • Logical volume size: Specify a value smaller than the volume group's available space, either in MB or GB.
      • Logical volume name: Specify a volume name, for example, lvdata1.
      • Volume group name: Specify the name of the volume group where the logical volume belongs.

      In this example, run the following command:

      lvcreate -L 15GB -n lvdata1 vgdata

      Information similar to the following is displayed:

      [root@ecs-lvmtest ~]# lvcreate -L 15GB -n lvdata1 vgdata
        Logical volume "lvdata1" created.

   2. Run the following command to query details of the logical volume:

      lvdisplay

      Information similar to the following is displayed:

      [root@ecs-lvmtest ~]# lvdisplay
        --- Logical volume ---
        LV Path                /dev/vgdata/lvdata1
        LV Name                lvdata1
        VG Name                vgdata
        LV UUID                c7mNcF-CdPW-5PLD-1gVj-QZpB-nHfy-PHXchV
        LV Write Access        read/write
        LV Creation host, time ecs-lvmtest.novalocal, 2018-11-29 11:28:18 +0800
        LV Status              available
        # open                 0
        LV Size                15.00 GiB
        Current LE             3840
        Segments               2
        Allocation             inherit
        Read ahead sectors     auto
        - currently set to     8192
        Block device           252:0