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Chapter 2. Managing LVM physical volumes

A physical volume (PV) is a physical storage device or a partition on a storage device that LVM uses.

During the initialization process, an LVM disk label and metadata are written to the device, which allows LVM to track and manage it as part of the logical volume management scheme.

Note

You cannot increase the size of the metadata after the initialization. If you need larger metadata, you must set the appropriate size during the initialization process.

When initialization process is complete, you can allocate the PV to a volume group (VG). You can divide this VG into logical volumes (LVs), which are the virtual block devices that operating systems and applications can use for storage.

To ensure optimal performance, partition the whole disk as a single PV for LVM use.

2.1. Creating an LVM physical volume

You can use the pvcreate command to initialize a physical volume LVM usage.

Prerequisites

  • Administrative access.
  • The lvm2 package is installed.

Procedure

  1. Identify the storage device you want to use as a physical volume. To list all available storage devices, use: 

    $ lsblk

  2. Create an LVM physical volume: 

    # pvcreate /dev/sdb

    Replace /dev/sdb with the name of the device you want to initialize as a physical volume.

Verification steps

  • Display the created physical volume: 

    # pvs

  PV         VG  Fmt  Attr PSize  PFree
  /dev/sdb       lvm2 a--  28.87g 13.87g

Additional resources

  • pvcreate(8), pvdisplay(8), pvs(8), pvscan(8), and lvm(8) man pages on your system

2.2. Removing LVM physical volumes

You can use the pvremove command to remove a physical volume for LVM usage.

Prerequisites

  • Administrative access.

Procedure

  1. List the physical volumes to identify the device you want to remove: 

    # pvs

  PV           VG Fmt  Attr PSize  PFree
  /dev/sdb1       lvm2 ---  28.87g 28.87g

  2. Remove the physical volume: 

    # pvremove /dev/sdb1

    Replace /dev/sdb1 with the name of the device associated with the physical volume.

Note

If your physical volume is part of the volume group, you need to remove it from the volume group first.

  • If you volume group contains more that one physical volume, use the vgreduce command: 

    # vgreduce VolumeGroupName /dev/sdb1

    Replace VolumeGroupName with the name of the volume group. Replace /dev/sdb1 with the name of the device.

  • If your volume group contains only one physical volume, use vgremove command: 

    # vgremove VolumeGroupName

    Replace VolumeGroupName with the name of the volume group.

Verification

  • Verify the physical volume is removed: 

    # pvs

Additional resources

  • pvremove(8) man page on your system

2.3. Creating logical volumes in the web console

Logical volumes act as physical drives. You can use the RHEL 8 web console to create LVM logical volumes in a volume group.

Prerequisites

  • You have installed the RHEL 8 web console.

    For instructions, see Installing and enabling the web console.

  • The cockpit-storaged package is installed on your system.
  • The volume group is created.

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Click Storage.
  3. In the Storage table, click the volume group in which you want to create logical volumes.
  4. On the Logical volume group page, scroll to the LVM2 logical volumes section and click Create new logical volume.
  5. In the Name field, enter a name for the new logical volume. Do not include spaces in the name.

  6. In the Purpose drop-down menu, select Block device for filesystems.

    This configuration enables you to create a logical volume with the maximum volume size which is equal to the sum of the capacities of all drives included in the volume group.

    cockpit lv block dev

  7. Define the size of the logical volume. Consider:

    • How much space the system using this logical volume will need.
    • How many logical volumes you want to create.

    You do not have to use the whole space. If necessary, you can grow the logical volume later.

    cockpit lv size

  8. Click Create.

    The logical volume is created. To use the logical volume you must format and mount the volume.

Verification

  • On the Logical volume page, scroll to the LVM2 logical volumes section and verify whether the new logical volume is listed.

    cockpit lv details

2.4. Formatting logical volumes in the web console

Logical volumes act as physical drives. To use them, you must format them with a file system.

Warning

Formatting logical volumes erases all data on the volume.

The file system you select determines the configuration parameters you can use for logical volumes. For example, the XFS file system does not support shrinking volumes.

Prerequisites

  • You have installed the RHEL 8 web console.

    For instructions, see Installing and enabling the web console.

  • The cockpit-storaged package is installed on your system.
  • The logical volume created.
  • You have root access privileges to the system.

Procedure

  1. Log in to the RHEL 8 web console.

    For details, see Logging in to the web console.

  2. Click Storage.
  3. In the Storage table, click the volume group in the logical volumes is created.
  4. On the Logical volume group page, scroll to the LVM2 logical volumes section.
  5. Click the menu button, ⋮, next to the volume group you want to format.

  6. From the drop-down menu, select Format.

    Image displaying the details of the existing logical volume.

  7. In the Name field, enter a name for the file system.

  8. In the Mount Point field, add the mount path.

    The format a logical volume dialog box with configurable fields.

  9. In the Type drop-down menu, select a file system:

    • XFS file system supports large logical volumes, switching physical drives online without outage, and growing an existing file system. Leave this file system selected if you do not have a different strong preference.

      XFS does not support reducing the size of a volume formatted with an XFS file system

    • ext4 file system supports:

      • Logical volumes
      • Switching physical drives online without an outage
      • Growing a file system
      • Shrinking a file system

  10. Select the Overwrite existing data with zeros checkbox if you want the RHEL web console to rewrite the whole disk with zeros. This option is slower because the program has to go through the whole disk, but it is more secure. Use this option if the disk includes any data and you need to overwrite it.

    If you do not select the Overwrite existing data with zeros checkbox, the RHEL web console rewrites only the disk header. This increases the speed of formatting.

  11. From the Encryption drop-down menu, select the type of encryption if you want to enable it on the logical volume.

    You can select a version with either the LUKS1 (Linux Unified Key Setup) or LUKS2 encryption, which allows you to encrypt the volume with a passphrase.

  12. In the At boot drop-down menu, select when you want the logical volume to mount after the system boots.
  13. Select the required Mount options.

  14. Format the logical volume:

    • If you want to format the volume and immediately mount it, click Format and mount.

    • If you want to format the volume without mounting it, click Format only.

      Formatting can take several minutes depending on the volume size and which formatting options are selected.

Verification

  1. On the Logical volume group page, scroll to the LVM2 logical volumes section and click the logical volume to check the details and additional options.

    cockpit lv formatted

  2. If you selected the Format only option, click the menu button at the end of the line of the logical volume, and select Mount to use the logical volume.

2.5. Resizing logical volumes in the web console

You can extend or reduce logical volumes in the RHEL 8 web console. The example procedure demonstrates how to grow and shrink the size of a logical volume without taking the volume offline.

Warning

You cannot reduce volumes that contains GFS2 or XFS filesystem.

Prerequisites

  • You have installed the RHEL 8 web console.

    For instructions, see Installing and enabling the web console.

  • The cockpit-storaged package is installed on your system.
  • An existing logical volume containing a file system that supports resizing logical volumes.

Procedure

  1. Log in to the RHEL web console.
  2. Click Storage.
  3. In the Storage table, click the volume group in the logical volumes is created.

  4. On the Logical volume group page, scroll to the LVM2 logical volumes section and click the menu button, ⋮, next to volume group you want to resize.

    LVM2 volume group details

  5. From the menu, select Grow or Shrink to resize the volume:

    • Growing the Volume:

      1. Select Grow to increase the size of the volume.

      2. In the Grow logical volume dialog box, adjust the size of the logical volume.

        LV grow dialog

      3. Click Grow.

        LVM grows the logical volume without causing a system outage.

    • Shrinking the Volume:

      1. Select Shrink to reduce the size of the volume.

      2. In the Shrink logical volume dialog box, adjust the size of the logical volume.

        LV shrink dialog

      3. Click Shrink.

        LVM shrinks the logical volume without causing a system outage.

2.6. Additional resources

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