Add/Remove PV on VG on the Fly

Linux Tutorials - Herong's Tutorial Examples

∟Add/Remove PV on VG on the Fly

Describes what is a VG (Volume Group) - a virtual storage device made up by one or more PVs (Physical Volumes). Tutorial examples are given on how to create a new VG, add PV to a VG and remove a PV from a VG.

What Is VG (Volume Group)? VG represents a virtual storage device made up by one or more PVs (Physical Volumes). Once created, a VG can be divided into one or more LVs (Logical Volumes) to hold different file systems.

There are a number commands provided on CentOS 8 systems for you to create and manage PVs.

1. List all VGs that are currently managed by LVM using the "pvs" command, which is a also sub-command of the "lvm" command. The output shows that I have 1 VG named as "cl" supported by 2 PVs and holding 3 LVs with 831.69g free space.

herong$ sudo vgs
  VG #PV #LV #SN Attr   VSize VFree
  cl   2   3   0 wz--n- 1.00t 831.69g

2. Display details of each VG using the "vgdisplay" command, which is also a sub-command of the "lvm" command. The output shows the VG's format is "lvm2".

herong$ sudo vgdisplay

  --- Volume group ---
  VG Name               cl
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  6
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               1.00 TiB
  PE Size               4.00 MiB
  Total PE              263256
  Alloc PE / Size       50343 / 196.65 GiB
  Free  PE / Size       212913 / 831.69 GiB
  VG UUID               C48qEx-RPFb-Xf5D-exff-0aVo-...

3. Display PVs and LVs that are related to the "cl" VG.

herong$ sudo pvs
  PV         VG Fmt  Attr PSize   PFree
  /dev/sda7  cl lvm2 a--   96.65g      0
  /dev/sdb2  cl lvm2 a--  931.69g 831.69g
  /dev/sdb3     lvm2 ---   93.13g  93.13g

herong$ sudo lvs
  LV   VG Attr       LSize   Pool Origin Data%  Meta%  ...
  home cl -wi-ao---- 138.94g
  root cl -wi-ao----  50.00g
  swap cl -wi-ao----   7.71g

How To Add PV to a VG? If an existing VG is running out of space, you can follow steps below to add a new PV to the VG.

1. Check available PVs using "pvs" command. I see /dev/sdb3 is a new PV with 93.13g of space.

herong$ sudo pvs
  PV         VG Fmt  Attr PSize   PFree
  /dev/sda7  cl lvm2 a--   96.65g      0
  /dev/sdb2  cl lvm2 a--  931.69g 831.69g
  /dev/sdb3     lvm2 ---   93.13g  93.13g

2. Check existing VGs using "vgs" command. I see "cl" is an existing VG with 2 PVs and 1.00t of space.

herong$ sudo vgs
  VG #PV #LV #SN Attr   VSize VFree
  cl   2   3   0 wz--n- 1.00t 831.69g

3. Add /dev/sdb3 to "cl" using "vgextend" command. The output shows "cl" is extended to 1.10t of space.

herong$ sudo vgextend cl /dev/sdb3
 Volume group "cl" successfully extended

herong$ sudo vgs
   VG #PV #LV #SN Attr   VSize  VFree
   cl   3   3   0 wz--n- 1.10t 924.82g

How To Remove PV from a VG? If a PV in a VG is not used at all, you can remove it from the VG.

1. Check to see if the PV is used or not. I see /dev/sdb3 with entire space marked as free. So it is not used.

herong$ sudo pvs
  PV         VG Fmt  Attr PSize   PFree
  /dev/sda7  cl lvm2 a--   96.65g      0
  /dev/sdb2  cl lvm2 a--  931.69g 831.69g
  /dev/sdb3  cl lvm2 a--   93.13g  93.13g

2. Remove /dev/sdb3 from "cl" using the "vgreduce" command.

herong$ sudo vgreduce cl /dev/sdb3
  Removed "/dev/sdb3" from volume group "cl"

herong$ sudo pvs
  PV         VG Fmt  Attr PSize   PFree
  /dev/sda7  cl lvm2 a--   96.65g      0
  /dev/sdb2  cl lvm2 a--  931.69g 831.69g
  /dev/sdb3     lvm2 ---   93.13g  93.13g

As you can see, managing PVs in a VG is easy. You can add a PV to a VG and remove it at any time, while the VG is still in use.

How To Create a New VG VG? If don't want to use the existing VG, you can create a new one.

1. Make sure that there is free PV available to used as the first PV for the new VG.

herong$ sudo pvs
  PV         VG Fmt  Attr PSize   PFree
  /dev/sda7  cl lvm2 a--   96.65g      0
  /dev/sdb2  cl lvm2 a--  931.69g 831.69g
  /dev/sdb3     lvm2 ---   93.13g  93.13g

2. Create a new VG with a free PV using "vgcreate" command.

herong$ sudo vgcreate data /dev/sdb3
  Volume group "data" successfully created

herong$ sudo pvs
  PV         VG   Fmt  Attr PSize   PFree
  /dev/sda7  cl   lvm2 a--   96.65g      0
  /dev/sdb2  cl   lvm2 a--  931.69g 831.69g
  /dev/sdb3  data lvm2 a--   93.13g  93.13g

herong$ sudo vgs
  VG   #PV #LV #SN Attr   VSize   VFree
  cl     2   3   0 wz--n-   1.00t 831.69g
  data   1   0   0 wz--n-  93.13g  93.13g