Chapter 5. Modifying the size of a logical volume
After you have created a logical volume, you can modify the size of the volume.
5.1. Growing a logical volume and file system
This procedure describes how to extend the logical volume and grow a file system on the same logical volume.
To increase the size of a logical volume, use the
lvextend command. When you extend the logical volume, you can indicate how much you want to extend the volume, or how large you want it to be after you extend it.
You have an existing logical volume (LV) with a file system on it. Determine the file system type by using the
For more information on creating LV and a file system, see Creating LVM logical volume.
You have sufficient space in the volume group to grow your LV and file system. Use the
vgs -o name,vgfreecommand to determine the available space.
Optional: If the volume group has insufficient space to grow your LV, then add a new physical volume to the volume group by using the following command:
# vgextend myvg /dev/vdb3 Physical volume "/dev/vdb3" successfully created. Volume group "myvg" successfully extended
For more information, see Creating LVM volume group.
Now that the volume group is large enough, execute any one of the following steps as per your requirement:
To extend the LV with the provided size, use the following command:
# lvextend -L 3G /dev/myvg/mylv Size of logical volume myvg/mylv changed from 2.00 GiB (512 extents) to 3.00 GiB (768 extents). Logical volume myvg/mylv successfully resized.Note
You can use the
-roption of the
lvextendcommand to extend the logical volume and resize the underlying file system with a single command:
# lvextend -r -L 3G /dev/myvg/mylvWarning
You can also extend the logical volume using the
lvresizecommand with the same arguments, but this command does not guarantee against accidental shrinkage.
To extend the mylv logical volume to fill all of the unallocated space in the myvg volume group, use the following command:
# lvextend -l +100%FREE /dev/myvg/mylv Size of logical volume myvg/mylv changed from 10.00 GiB (2560 extents) to 6.35 TiB (1665465 extents). Logical volume myvg/mylv successfully resized.
As with the
lvcreatecommand, you can use the
-largument of the
lvextendcommand to specify the number of extents by which to increase the size of the logical volume. You can also use this argument to specify a percentage of the volume group, or a percentage of the remaining free space in the volume group.
If you are not using the
roption with the
lvextendcommand to extend the LV and resize the file system with a single command, then resize the file system on the logical volume by using the following command:
xfs_growfs /mnt/mnt1/ meta-data=/dev/mapper/myvg-mylv isize=512 agcount=4, agsize=65536 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=0 = reflink=1 data = bsize=4096 blocks=262144, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1 log =internal log bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 data blocks changed from 262144 to 524288Note
xfs_growfsgrows the file system to the maximum size supported by the underlying device. For more information, see Increasing the size of an XFS file system.
For resizing an ext4 file system, see Resizing an ext4 file system.
Verify if the file system is growing by using the following command:
# df -Th Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm tmpfs tmpfs 1.9G 8.6M 1.9G 1% /run tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup /dev/mapper/rhel-root xfs 45G 3.7G 42G 9% / /dev/vda1 xfs 1014M 369M 646M 37% /boot tmpfs tmpfs 374M 0 374M 0% /run/user/0 /dev/mapper/myvg-mylv xfs 2.0G 47M 2.0G 3% /mnt/mnt1
5.2. Shrinking logical volumes
You can reduce the size of a logical volume with the
Shrinking is not supported on a GFS2 or XFS file system, so you cannot reduce the size of a logical volume that contains a GFS2 or XFS file system.
If the logical volume you are reducing contains a file system, to prevent data loss you must ensure that the file system is not using the space in the logical volume that is being reduced. For this reason, it is recommended that you use the
--resizefs option of the
lvreduce command when the logical volume contains a file system.
When you use this option, the
lvreduce command attempts to reduce the file system before shrinking the logical volume. If shrinking the file system fails, as can occur if the file system is full or the file system does not support shrinking, then the
lvreduce command will fail and not attempt to shrink the logical volume.
In most cases, the
lvreduce command warns about possible data loss and asks for a confirmation. However, you should not rely on these confirmation prompts to prevent data loss because in some cases you will not see these prompts, such as when the logical volume is inactive or the
--resizefs option is not used.
Note that using the
--test option of the
lvreduce command does not indicate where the operation is safe, as this option does not check the file system or test the file system resize.
To shrink the mylv logical volume in myvg volume group to 64 megabytes, use the following command:
# lvreduce --resizefs -L 64M myvg/mylv fsck from util-linux 2.37.2 /dev/mapper/myvg-mylv: clean, 11/25688 files, 4800/102400 blocks resize2fs 1.46.2 (28-Feb-2021) Resizing the filesystem on /dev/mapper/myvg-mylv to 65536 (1k) blocks. The filesystem on /dev/mapper/myvg-mylv is now 65536 (1k) blocks long. Size of logical volume myvg/mylv changed from 100.00 MiB (25 extents) to 64.00 MiB (16 extents). Logical volume myvg/mylv successfully resized.
In this example, mylv contains a file system, which this command resizes together with the logical volume.
-sign before the resize value indicates that the value will be subtracted from the logical volume’s actual size. To shrink a logical volume to an absolute size of 64 megabytes, use the following command:
# lvreduce --resizefs -L -64M myvg/mylv
5.3. Extending a striped logical volume
In order to increase the size of a striped logical volume, there must be enough free space on the underlying physical volumes that make up the volume group to support the stripe. For example, if you have a two-way stripe that that uses up an entire volume group, adding a single physical volume to the volume group will not enable you to extend the stripe. Instead, you must add at least two physical volumes to the volume group.
For example, consider a volume group
vg that consists of two underlying physical volumes, as displayed with the following
vgsVG #PV #LV #SN Attr VSize VFree vg 2 0 0 wz--n- 271.31G 271.31G
You can create a stripe using the entire amount of space in the volume group.
lvcreate -n stripe1 -L 271.31G -i 2 vgUsing default stripesize 64.00 KB Rounding up size to full physical extent 271.31 GB Logical volume "stripe1" created #
lvs -a -o +devicesLV VG Attr LSize Origin Snap% Move Log Copy% Devices stripe1 vg -wi-a- 271.31G /dev/sda1(0),/dev/sdb1(0)
Note that the volume group now has no more free space.
vgsVG #PV #LV #SN Attr VSize VFree vg 2 1 0 wz--n- 271.31G 0
The following command adds another physical volume to the volume group, which then has 135 gigabytes of additional space.
vgextend vg /dev/sdc1Volume group "vg" successfully extended #
vgsVG #PV #LV #SN Attr VSize VFree vg 3 1 0 wz--n- 406.97G 135.66G
At this point you cannot extend the striped logical volume to the full size of the volume group, because two underlying devices are needed in order to stripe the data.
lvextend vg/stripe1 -L 406GUsing stripesize of last segment 64.00 KB Extending logical volume stripe1 to 406.00 GB Insufficient suitable allocatable extents for logical volume stripe1: 34480 more required
To extend the striped logical volume, add another physical volume and then extend the logical volume. In this example, having added two physical volumes to the volume group we can extend the logical volume to the full size of the volume group.
vgextend vg /dev/sdd1Volume group "vg" successfully extended #
vgsVG #PV #LV #SN Attr VSize VFree vg 4 1 0 wz--n- 542.62G 271.31G #
lvextend vg/stripe1 -L 542GUsing stripesize of last segment 64.00 KB Extending logical volume stripe1 to 542.00 GB Logical volume stripe1 successfully resized
If you do not have enough underlying physical devices to extend the striped logical volume, it is possible to extend the volume anyway if it does not matter that the extension is not striped, which may result in uneven performance. When adding space to the logical volume, the default operation is to use the same striping parameters of the last segment of the existing logical volume, but you can override those parameters. The following example extends the existing striped logical volume to use the remaining free space after the initial
lvextend command fails.
lvextend vg/stripe1 -L 406GUsing stripesize of last segment 64.00 KB Extending logical volume stripe1 to 406.00 GB Insufficient suitable allocatable extents for logical volume stripe1: 34480 more required #
lvextend -i1 -l+100%FREE vg/stripe1