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How to Increase the Size of a Linux LVM by Adding a New Disk

Summary

This article will explain in detail how to add a new virtual disk to an existing VM and add the storage to the existing logical volume so it can be utilized as one large disk.

Adding a New Virtual Disk

Open XCP-ng Center and do the following:

  • Select the VM the virtual disk will be added to.
  • Click on the Storage tab and click Add...
  • Give the new disk a name and select the amount of storage in GB, then click Add.
  • Take note of the device path for the new disk
  • ex. /dev/xvdb
  • The disk should be detected automatically from within the VM, but in case it doesn't, reboot the VM.

Partition the New Disk

We now need to partition the new /dev/xvdb disk so that it can be used. This is done by using fdisk -l, which will confirm the correct path for the disk and output the following:

[root@xen-plex][~]
└──╼ #fdisk -l
Disk /dev/xvda: 2 TiB, 2147483648000 bytes, 4194304000 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x5ad16edb

Device     Boot   Start        End    Sectors  Size Id Type
/dev/xvda1         2048    1499135    1497088  731M 83 Linux
/dev/xvda2      1501182 4194303999 4192802818    2T  5 Extended
/dev/xvda5      1501184 4194303999 4192802816    2T 8e Linux LVM




Disk /dev/mapper/ubuntu--vg-root: 2 TiB, 2145688485888 bytes, 4190797824 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/ubuntu--vg-swap_1: 976 MiB, 1023410176 bytes, 1998848 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/xvdb: 1.5 TiB, 1610612736000 bytes, 3145728000 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 127CFA13-9DC6-4366-93C6-B36B5134C371

Now run fdisk again, but add the path to the disk.

  • Use 'n' to add a new partition and select 1 for the Partition number.
  • Use the defaults for First and Last sector.
  • Use ‘t’ to change to a partitions system ID. In this case, this can be set to ’1′ automatically as this is currently the only partition.
  • For the Hex Code, since this disk will be added to the existing logical volume, the Id can be noted from the Linux LVM listed above:
Device     Boot   Start        End    Sectors  Size Id Type
/dev/xvda1         2048    1499135    1497088  731M 83 Linux
/dev/xvda2      1501182 4194303999 4192802818    2T  5 Extended
/dev/xvda5      1501184 4194303999 4192802816    2T 8e Linux LVM
  • In this case, use the Hex Code for /dev/xvda5.
  • Use 'w' for writing the table to the disk. This will also close fdisk.

All the above steps should read like the following:

[root@xen-plex][~]
└──╼ #fdisk /dev/xvdb 

Welcome to fdisk (util-linux 2.27.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): n
Partition number (1-128, default 1): 1
First sector (34-3145727966, default 2048): 
Last sector, +sectors or +size{K,M,G,T,P} (2048-3145727966, default 3145727966): 

Created a new partition 1 of type 'Linux filesystem' and of size 1.5 TiB.

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): 8e
Type of partition 1 is unchanged: Linux filesystem.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

Increasing the Logical Volume

A physical volume will also need to be created to be added to the logical volume. This can be done with the pvcreate command.

┌─[root@xen-plex][~]
└──╼ #pvcreate /dev/xvdb1
  Physical volume "/dev/xvdb1" successfully created

Now confirm the name of the current volume group using the vgdisplay command. The real focus will be on the VG Name line for the rest of this article.

[root@xen-plex][~]
└──╼ #vgdisplay
  --- Volume group ---
  VG Name               ubuntu-vg
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  8
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               1.95 TiB
  PE Size               4.00 MiB
  Total PE              511816
  Alloc PE / Size       511816 / 1.95 TiB
  Free  PE / Size       0 / 0   
  VG UUID               EbOeff-YgpZ-f1w5-8HUh-ZScb-8pIH-i0ftwn

The vgextend command can now be used to extend the volume group by adding the physical volume of /dev/xvdb1.

[root@xen-plex][~]
└──╼ #vgextend ubuntu-vg /dev/xvdb1
  Volume group "ubuntu-vg" successfully extended

Use the pvscan command to scan all the disks for physical volumes. The result of the scan should list the original volume of /dev/xvda5 and the newer volume of /dev/xvdb1.

[root@xen-plex][~]
└──╼ #pvscan
  PV /dev/xvda5   VG ubuntu-vg       lvm2 [1.95 TiB / 0    free]
  PV /dev/xvdb1   VG ubuntu-vg       lvm2 [1.46 TiB / 1.46 TiB free]
  Total: 2 [3.42 TiB] / in use: 2 [3.42 TiB] / in no VG: 0 [0   ]

Finally, confirm the name of the logical volume using the lvdisplay command.

[root@xen-plex][~]
└──╼ #lvdisplay
  --- Logical volume ---
  LV Path                /dev/ubuntu-vg/root
  LV Name                root
  VG Name                ubuntu-vg
  LV UUID                VrCKdY-vEA8-WFRd-gisu-XD9Z-LFDQ-XGFdfq
  LV Write Access        read/write
  LV Creation host, time ubuntu, 2019-04-12 00:18:59 -0400
  LV Status              available
  # open                 1
  LV Size                1.95 TiB
  Current LE             511572
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

The logical volume will now need to be extended using the lvextend command. This will extend the original volume of /dev/xvda5 over the newer volume of /dev/xvdb1.

[root@xen-plex][~]
└──╼ #lvextend /dev/ubuntu-vg/root /dev/xvdb1 
  Size of logical volume ubuntu-vg/root changed from 1.95 TiB (511572 extents) to 3.42 TiB (895571 extents).
  Logical volume root successfully resized.

Run the lvdisplay command again, which should now display the increased volume size from both volumes, now one volume.

[root@xen-plex][~]
└──╼ #lvdisplay
  --- Logical volume ---
  LV Path                /dev/ubuntu-vg/root
  LV Name                root
  VG Name                ubuntu-vg
  LV UUID                VrCKdY-vEA8-WFRd-gisu-XD9Z-LFDQ-XGFdfq
  LV Write Access        read/write
  LV Creation host, time ubuntu, 2019-04-12 00:18:59 -0400
  LV Status              available
  # open                 1
  LV Size                3.42 TiB
  Current LE             895571
  Segments               3
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

Although the volume is now listing the correct volume size, that size is not yet usable until the resize2fs command is run. This will allow the system to make use of this new space.

[root@xen-plex][~]
└──╼ #resize2fs /dev/ubuntu-vg/root 
resize2fs 1.42.13 (17-May-2015)
Filesystem at /dev/ubuntu-vg/root is mounted on /; on-line resizing required
old_desc_blocks = 125, new_desc_blocks = 219
The filesystem on /dev/ubuntu-vg/root is now 917064704 (4k) blocks long.

The LVM has now been properly resized and is now usable by the VM. This can be confirmed with the df -h command, making note of the volume group - /dev/mapper/ubuntu--vg-root.

[root@xen-plex][~]
└──╼ #df -h
Filesystem                   Size  Used Avail Use% Mounted on
udev                         7.8G     0  7.8G   0% /dev
tmpfs                        1.6G  9.2M  1.6G   1% /run
/dev/mapper/ubuntu--vg-root  3.4T  1.4T  1.9T  41% /
tmpfs                        7.9G  120K  7.9G   1% /dev/shm
tmpfs                        5.0M     0  5.0M   0% /run/lock
tmpfs                        7.9G     0  7.9G   0% /sys/fs/cgroup
/dev/xvda1                   720M  141M  543M  21% /boot
192.168.1.6:/volume1/Plex     15T  6.3T  8.1T  44% /mnt/Plex
tmpfs                        1.6G   56K  1.6G   1% /run/user/1000

References

https://www.rootusers.com/how-to-increase-the-size-of-a-linux-lvm-by-adding-a-new-disk/