New LVM pool in existing volume group

These commands show how you can create a new LVM pool in an existing volume group. Virsh from libvirt is used for the task.
I’ve tested everything on a fresh Ubuntu Server 14.04 (Trusty Tahr).

How we start

During the installation of this server, I created 1 large volume group which spanned almost the whole disk ( except for /boot which sits on its own primary partition ). That single volume group lives in partition 2.

root@flipflop ~ # sgdisk -p /dev/sda
Disk /dev/sda: 5860533168 sectors, 2.7 TiB
Logical sector size: 512 bytes
Disk identifier (GUID): D09D3D4B-01CE-4A1F-8ED0-4E68253A85D6
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 5860533134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            4096         1052671   512.0 MiB   FD00  
   2         1052672      5860533134   2.7 TiB     FD00  
   3            2048            4095   1024.0 KiB  EF02  
root@flipflop ~ #

The installer of Ubuntu created this partition table. Note that we’re using a Guid Partition Table (GPT). A normal MBR is not possible anymore since the disk is over 2TB in size. In this partition, a Logical Volume Group (LVM) has been created.

root@flipflop ~ # vgdisplay
  --- Volume group ---
  VG Name               vg0
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                4
  Open LV               4
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               2.73 TiB
  PE Size               4.00 MiB
  Total PE              715236
  Alloc PE / Size       143872 / 562.00 GiB
  Free  PE / Size       571364 / 2.18 TiB
  VG UUID               YOVLIn-I0bX-0bND-JhuX-EnxI-YuO8-5ux86P
root@flipflop ~ #

Defining the new storage pool

To define the storage pool, I’m using the virsh command from libvirt with the pool-define-as option.
If you want to see all options, issue this command.

root@flipflop ~ # virsh help pool-define-as

To define the actual pool, I’ve run this command.

root@flipflop ~ # virsh pool-define-as mylvmpool logical - - /dev/sda2 vg0 /dev/vg0

This command defines the pool. There is no need to run ‘virsh pool-create’ because the pool already exists.
If you want to autostart the storage pool.

root@flipflop ~ # virsh pool-autostart mylvmpool

Checking the storage pool

Right now we can manipulate the vg using the virsh command. A couple of examples:

  • Listing all storage pools
  • root@flipflop ~ # virsh pool-list
     Name                 State      Autostart 
     mylvmpool            active     yes
  • Getting detailed info about a storage pool
  • root@flipflop ~ # virsh pool-info mylvmpool
    Name:           mylvmpool
    UUID:           cf2438fa-eeb7-457d-ae48-7c05f3cc8dc8
    State:          running
    Persistent:     yes
    Autostart:      yes
    Capacity:       2.73 TiB
    Allocation:     562.00 GiB
    Available:      2.18 TiB
  • Listing all volumes in the storage pool
  • root@flipflop ~ # virsh vol-list mylvmpool
     Name                 Path                                    
     home                 /dev/vg0/home                                             
     root                 /dev/vg0/root                           
     swap                 /dev/vg0/swap
  • Creating a new volume
  • root@flipflop ~ # virsh vol-create-as mylvmpool newvol 100G
    Vol newvol created
  • Checking if the volume has been created
  • root@flipflop ~ # virsh vol-list mylvmpool
     Name                 Path                                    
     home                 /dev/vg0/home                                         
     newvol               /dev/vg0/newvol                         
     root                 /dev/vg0/root                           
     swap                 /dev/vg0/swap
  • Listing the details of the new volume
  • root@flipflop ~ # virsh vol-info newvol --pool mylvmpool
    Name:           newvol
    Type:           block
    Capacity:       100.00 GiB
    Allocation:     100.00 GiB
  • Deleting the new volume
  • root@flipflop ~ # virsh vol-delete newvol --pool mylvmpool
    Vol newvol deleted

    This post explained how to create a new LVM storage pool in an existing Logical Volume Group. It also show how volumes can be listed, created and deleted.

    2 thoughts on “New LVM pool in existing volume group

    1. Pingback: Migrating from file to lvm storage - Thomas Elsen Security Blog

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