Scenarios

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

Multiple EVS disks with different specifications can be used to create logical volumes.

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

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 query and take note of the disk 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. Run the following command to create physical volumes based on the 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.

   For 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.

4. 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.

5. 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 descriptions:

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

   For 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

6. 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

7. Run the following command to create a logical volume:

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

   Parameter descriptions:

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

   For 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.

8. 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