13.4. LVM-based Storage Pools

⁠13.4. LVM-based Storage Pools

This chapter covers using LVM volume groups as storage pools.

LVM-based storage groups provide the full flexibility of LVM.

Note

Thin provisioning is currently not possible with LVM based storage pools.

Note

For more details on LVM, refer to the Red Hat Enterprise Linux Storage Administration Guide.

Warning

LVM-based storage pools require a full disk partition. If activating a new partition/device with these procedures, the partition will be formatted and all data will be erased. If using the host's existing Volume Group (VG) nothing will be erased. It is recommended to back up the storage device before commencing the following procedure.

⁠13.4.1. Creating an LVM-based Storage Pool with virt-manager

LVM-based storage pools can use existing LVM volume groups or create new LVM volume groups on a blank partition.

Optional: Create new partition for LVM volumes
These steps describe how to create a new partition and LVM volume group on a new hard disk drive.
Warning
This procedure will remove all data from the selected storage device.
1. Create a new partition
  Use the fdisk command to create a new disk partition from the command line. The following example creates a new partition that uses the entire disk on the storage device /dev/sdb.
```
# fdisk /dev/sdb
Command (m for help):
```
  Press n for a new partition.
2. Press p for a primary partition.
```
Command action
   e   extended
   p   primary partition (1-4)
```
3. Choose an available partition number. In this example the first partition is chosen by entering 1.
```
Partition number (1-4): 1
```
4. Enter the default first cylinder by pressing Enter.
```
First cylinder (1-400, default 1):
```
5. Select the size of the partition. In this example the entire disk is allocated by pressing Enter.
```
Last cylinder or +size or +sizeM or +sizeK (2-400, default 400):
```
6. Set the type of partition by pressing t.
```
Command (m for help): t
```
7. Choose the partition you created in the previous steps. In this example, the partition number is 1.
```
Partition number (1-4): 1
```
8. Enter 8e for a Linux LVM partition.
```
Hex code (type L to list codes): 8e
```
9. write changes to disk and quit.
```
Command (m for help): w
Command (m for help): q
```
10. Create a new LVM volume group
  Create a new LVM volume group with the vgcreate command. This example creates a volume group named guest_images_lvm.
```
# vgcreate guest_images_lvm /dev/sdb1
  Physical volume "/dev/vdb1" successfully created
  Volume group "guest_images_lvm" successfully created
```
The new LVM volume group, guest_images_lvm, can now be used for an LVM-based storage pool.
Open the storage pool settings
1. In the virt-manager graphical interface, select the host from the main window.
  Open the Edit menu and select Connection Details
2. click the Storage tab.
  ⁠
  Figure 13.9. Storage tab
Create the new storage pool
1. Start the Wizard
  Press the + button (the add pool button). The Add a New Storage Pool wizard appears.
  Choose a Name for the storage pool. We use guest_images_lvm for this example. Then change the Type to logical: LVM Volume Group, and
  ⁠
  Figure 13.10. Add LVM storage pool
  Press Forward to continue.
2. Add a new pool (part 2)
  Fill in the Target Path and Source Path fields, and check the Build Pool check box.
  - Use the Target Path field to either select an existing LVM volume group or as the name for a new volume group. The default format is storage_pool_name/lvm_Volume_Group_name.
    This example uses a new volume group named /dev/guest_images_lvm.
  - The Source Path field is optional if an existing LVM volume group is used in the Target Path.
    For new LVM volume groups, input the location of a storage device in the Source Path field. This example uses a blank partition /dev/sdc.
  - The Build Pool check box instructs virt-manager to create a new LVM volume group. If you are using an existing volume group you should not select the Build Pool check box.
    This example is using a blank partition to create a new volume group so the Build Pool check box must be selected.
  ⁠
  Figure 13.11. Add target and source
  Verify the details and press the Finish button format the LVM volume group and create the storage pool.
3. Confirm the device to be formatted
  A warning message appears.
  ⁠
  Figure 13.12. Warning message
  Press the Yes button to proceed to erase all data on the storage device and create the storage pool.
Verify the new storage pool
The new storage pool will appear in the list on the left after a few seconds. Verify the details are what you expect, 465.76 GB Free in our example. Also verify the State field reports the new storage pool as Active.
It is generally a good idea to have the Autostart check box enabled, to ensure the storage pool starts automatically with libvirtd.
⁠
Figure 13.13. Confirm LVM storage pool details
Close the Connection Details dialog, as the task is now complete.

⁠13.4.2. Deleting a Storage Pool Using virt-manager

This procedure demonstrates how to delete a storage pool.

To avoid any issues with other guest virtual machines using the same pool, it is best to stop the storage pool and release any resources in use by it. To do this, select the storage pool you want to stop and click .
⁠
Figure 13.14. Stop Icon
Delete the storage pool by clicking . This icon is only enabled if you stop the storage pool first.

⁠13.4.3. Creating an LVM-based Storage Pool with virsh

This section outlines the steps required to create an LVM-based storage pool with the virsh command. It uses the example of a pool named guest_images_lvm from a single drive (/dev/sdc). This is only an example and your settings should be substituted as appropriate.

⁠

Procedure 13.3. Creating an LVM-based storage pool with virsh

Define the pool name guest_images_lvm.

# virsh pool-define-as guest_images_lvm logical - - /dev/sdc libvirt_lvm \ /dev/libvirt_lvm
Pool guest_images_lvm defined

Build the pool according to the specified name. If you are using an already existing volume group, skip this step.
```
# virsh pool-build guest_images_lvm

Pool guest_images_lvm built
```

Initialize the new pool.

# virsh pool-start guest_images_lvm

Pool guest_images_lvm started

Show the volume group information with the vgs command.

# vgs
VG          #PV #LV #SN Attr   VSize   VFree
libvirt_lvm   1   0   0 wz--n- 465.76g 465.76g

Set the pool to start automatically.

# virsh pool-autostart guest_images_lvm
Pool guest_images_lvm marked as autostarted

List the available pools with the virsh command.

# virsh pool-list --all
Name                 State      Autostart
-----------------------------------------
default              active     yes
guest_images_lvm     active     yes

The following commands demonstrate the creation of three volumes (volume1, volume2 and volume3) within this pool.

# virsh vol-create-as guest_images_lvm volume1 8G
Vol volume1 created

# virsh vol-create-as guest_images_lvm volume2 8G
Vol volume2 created

# virsh vol-create-as guest_images_lvm volume3 8G
Vol volume3 created

List the available volumes in this pool with the virsh command.

# virsh vol-list guest_images_lvm
Name                 Path
-----------------------------------------
volume1              /dev/libvirt_lvm/volume1
volume2              /dev/libvirt_lvm/volume2
volume3              /dev/libvirt_lvm/volume3

The following two commands (lvscan and lvs) display further information about the newly created volumes.

# lvscan
ACTIVE            '/dev/libvirt_lvm/volume1' [8.00 GiB] inherit
ACTIVE            '/dev/libvirt_lvm/volume2' [8.00 GiB] inherit
ACTIVE            '/dev/libvirt_lvm/volume3' [8.00 GiB] inherit

# lvs
LV       VG            Attr     LSize   Pool Origin Data%  Move Log Copy%  Convert
volume1  libvirt_lvm   -wi-a-   8.00g
volume2  libvirt_lvm   -wi-a-   8.00g
volume3  libvirt_lvm   -wi-a-   8.00g

⁠13.4.4. Deleting a Storage Pool Using virsh

The following demonstrates how to delete a storage pool using virsh:

To avoid any issues with other guests using the same pool, it is best to stop the storage pool and release any resources in use by it.
```
# virsh pool-destroy guest_images_disk
```
Optionally, if you want to remove the directory where the storage pool resides use the following command:
```
# virsh pool-delete guest_images_disk
```
Remove the storage pool's definition
```
# virsh pool-undefine guest_images_disk
```