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Manage Storage Volumes

As described in the previous guide on the system installation, the LVM is a flexible and powerful storage management system. It delivers excellent functionality. However, by default, it initially only allocates 100GB of storage for the logical volume.

The default allocation ensures ample storage for basic system functionality without consuming the entire available storage capacity. This approach allows users to extend the storage volumes as needed based on their specific requirements and the growth of their data.

One of the main reasons for this conservative allocation is that it is much easier to extend storage volumes than shrink them. Shrinking volumes can be more complicated and time-consuming, often requiring unmounting and remounting of the filesystems and a greater risk of data loss. By starting with a smaller allocation, LVM allows you to manage your storage more efficiently.

As we use the server as the primary node machine, we want to extend the capacity of 100 GB to the total size of the physical storage before even the physical storage space is no longer sufficient and new hard disks must be added.

Before we add or extend any storage volumes, we have to check the volume group's status.

If you already set your logical volume to the maximum capacity during the installation, looking at the following section is still recommended. You will learn the basics about LVM when adding a new storage device.

3.2.1 Checking the volume group​

Using the volume group and logical volume display commands, we can track information about the existing volume groups of LVM and their logical volumes on these groups. It provides details on the properties, such as the VG name, total size, free size, and the number of physical and logical volumes it contains.

sudo vgdisplay

If you never changed the LVM settings during installation, the output and volume group name should look similar to this:

  --- Volume group ---
  VG Name               ubuntu-vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               [VOLUME_GROUP_SIZE]
  PE Size               4.00 MiB
  Total PE              [TOTAL_PE]
  Alloc PE / Size       [ALLOCATED_PE] / 100.00 GiB
  Free  PE / Size       [FREE_PE] / [FREE_DISK_SPACE]
  VG UUID               [VOLUME_GROUP_UNIVERSALLY_UNIQUE_IDENTIFIER]

Remember that the VG Name property might differ if you gave a custom name during the installation. If you did not create a second one during the installation, there should only be one volume group for now.

Physical Extents​

When a physical volume is added to a volume group, the disk space in the physical volume is divided into Physical Extents. The size of the physical extent is determined when the volume group is created, and all extents within a group are the same size.

They are portions of disk space on a physical volume, usually several megabytes.

  • Total Physical Extents: Total Number of Physical Extents allocated or free across all volumes.
  • Alloc Physical Extents / Size: displays how much space has been allocated by the logical volume.
  • Free Physical Extents / Size: displays how much accessible space units are left on the physical volume. If it is already zero, no more physical free disk space is left.

Check the amount of free disk space left on the physical volume. If you did not already extend the disk size during the installation, there should be plenty of storage left that we can add to the logical volume of the group.

If you extended your logical volume to the maximum available capacity during installation, the Free PE / Size property will show 0 / 0 , meaning no more unreserved storage is left on the volume group for any partition to utilize.

Checking disk usage​

You can use the disk filesystem command to check your disk usage on the logical volume. The -h flag will print the outcomes in a human-readable format.

df -h

The outcome should look similar to the following. Keep in mind sizes can be different on your end. Check the size of your volume group mounted on /. If you did not extend your logical volume size yet, the size of it would show as 100G. The node install takes up about 11GB for now.

Filesystem                         Size  Used Avail Use% Mounted on
tmpfs                              3.2G  1.6M  3.2G   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv  1.8T   11G  100G  11% /
tmpfs                               16G     0   16G   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
/dev/nvme0n1p2                     2.0G  131M  1.7G   8% /boot
/dev/nvme0n1p1                     1.1G  6.1M  1.1G   1% /boot/efi
tmpfs                              3.2G  4.0K  3.2G   1% /run/user/1000

If your storage is getting full or you want to allocate more space to your main disk, you can add a new disk or extend the main logical volume in the next steps.

3.2.2 Adding a new disk to the group​

In case you have a second storage device, like a 2.5" HHD that you want to add to your node, you can do this by extending the logical volume and the volume group itself across multiple physical devices. Have a look into the hardware build section for more information about adding the HHD to your file.

If you add more storage after the node is running, stop all blockchain processes and shut down the node properly using the sudo shutdown now command. Then open the case and connect your new storage on the corresponding frame.

First, we have to get the identifier of your newly added device. We can use the list block command tool. It displays information about all block devices, which are particular files representing storage devices that handle data as blocks, such as hard drives, SSDs, and optical drives.

lsblk

The output should look similar if you have an NVM SSD and a 2.5" HDD. Keep in mind that the numbers of storage will be different. You can add any storage you like.

NAME                      MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0                       7:0    0  63.3M  1 loop /snap/core20/1822
loop1                       7:1    0  63.3M  1 loop /snap/core20/1879
loop2                       7:2    0 111.9M  1 loop /snap/lxd/24322
loop3                       7:3    0  49.8M  1 loop /snap/snapd/18357
loop4                       7:4    0  53.2M  1 loop /snap/snapd/19122
nvme0n1                   259:0    0   1.8T  0 disk
├─nvme0n1p1               259:1    0     1G  0 part /boot/efi
├─nvme0n1p2               259:2    0     2G  0 part /boot
└─nvme0n1p3               259:3    0   1.8T  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0   1.8T  0 lvm  /
sda                         8:0    0   7.8T  0 disk

For the above example:

  • nvme0n1 is the disk identifier of the SSD used as the primary storage
  • sda is the disk identifier of the HDD used as additional storage

Initializing the disk​

To initialize the new disk so that it can be used as a physical volume, we can use the LVM tool to create physical volumes:

sudo pvcreate /dev/<disk-identifier>

Creating a multi-device volume group​

Afterward, we can extend our existing volume group to include this new physical volume on top of the initial SSD's space. Therefore, we can use the volume group extension tool. We will have to input the volume group's name and the path to the newly added physical volume that we want to add.

sudo vgextend <volume-group-name> /dev/<disk-identifier>

Next, we can recheck the volume group to verify if the group grew in storage size:

sudo vgdisplay

If you never changed the LVM settings during installation, the output and volume group name should look similar to this:

  --- Volume group ---
  VG Name               ubuntu-vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               [VOLUME_GROUP_SIZE]
  PE Size               4.00 MiB
  Total PE              [TOTAL_PE]
  Alloc PE / Size       [ALLOCATED_PE] / [LOGICAL_VOLUME_SIZE]
  Free  PE / Size       [FREE_PE] / [FREE_DISK_SPACE]
  VG UUID               [VOLUME_GROUP_UNIVERSALLY_UNIQUE_IDENTIFIER]

After extending the group to use the space on the newly added physical volume, the Free PE / Size property should have plenty of free extents to add to our logical volume so we can use the space on our node.

3.2.3 Checking the logical volumes​

Before adding space to our logical volume, we have to check the properties of the logical volumes available on the device.

sudo lvdisplay

If you never changed the LVM settings during installation, the output and volume group name should look similar to this:

  --- Logical volume ---
  LV Path                /dev/ubuntu-vg/ubuntu-lv
  LV Name                ubuntu-lv
  VG Name                ubuntu-vg
  LV UUID                [LOGICAL_VOLUME_UNIVERSALLY_UNIQUE_IDENTIFIER]
  LV Write Access        read/write
  LV Creation host, time ubuntu-server, [CREATION_DATE] +0000
  LV Status              available
  # open                 1
  LV Size                <100.00 GiB
  Current LE             [NUMBER_OF_LOGICAL_EXTENTS]
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

Remember that the LV Path, LV Name, and VG Name properties might differ if you have been given a custom name during installation. If you did not create a second one during the installation, there should only be one logical volume for now.

If you extended your logical volume to the maximum available capacity on the main storage device during installation, the LV Size property will be similar to the size of your first physical disk.

3.2.4 Extending a logical volume​

LVM itself comes with its toolkit on Unix-like operating systems used to increase the size of a logical volume. We can pass the following arguments:

  • -l: the flag specifies the size that should be given to the logical volume in extent. We can use the +100%FREE parameter to tell the extension tool to use all the free Physical Extents in the volume group. It will then effectively extend the logical volume to use the remaining free space in the volume group. Use a lower amount to expand a volume group by a lower percentage.
  • -L: the flag specifies the size that should be given to the logical volume in gigabytes. We can use the +50G parameter to tell the extension tool to add 50 GB to the volume group. It will then effectively extend the logical volume to use the remaining free space in the volume group. Change the number before the G to expand a volume group by a different amount. For extending smaller or more significant amounts, you can use M for megabytes and T for terabytes.
  • path: the parameter defines the logical volume you want to extend on the volume group. Update the <logical-volume-path> with the LV Path property from the previous lvdisplay command.

If you did not extend the storage to the physically available space during installation but want to configure it now, you can use the following command. The expansion can be done for the main storage device and the newly added logical volume of the secondary storage disk.

sudo lvextend -l +100%FREE <logical-volume-path>

The output should look like the following:

  Size of logical volume <volume-group-name>/<logical-volume-name> changed from [INITIAL_STORAGE_SPACE] GiB ([ALLOCATED_PE] extents) to [FINAL_STORAGE_SPACE] ([TOTAL_PE] extents).
  Logical volume <volume-group-name>/<logical-volume-name> successfully resized.

After running this command, the file system on the logical volume needs to be resized to take advantage of the newly added space.

3.2.5 Resizing a volume group​

LVM itself has a utility that allows you to resize Linux file systems. It can be used to increase or decrease the size of an existing file system. We can pass the device file representing the logical volume we want to resize.

sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv

When resize2fs command is called without specifying a new size, it will default to resizing the file system to take up all available space on the device we extended before.

The output should look like the following:

resize2fs 1.46.5 ([DATE])
Filesystem at /dev/mapper/ubuntu--vg-ubuntu--lv is mounted on /; on-line resizing required
old_desc_blocks = [DESC_BLOCKS], new_desc_blocks = [NEW_DESC_BLOCKS]
The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now [TOTAL_BLOCKS] ([BLOCK_NUMBER]) blocks long.

Descriptor Blocks Usage​

File systems have two key components: index nodes and descriptor blocks.

  • Index Nodes are data structures within a filesystem that contain information about a file or directory, such as its size, owner, and access rights. Every file or directory has an associated inode, which essentially serves as a table of contents for the file's data.
  • Descriptor Blocks are part of the filesystem's metadata. They contain information about where the file data is located on the disk and keep track of arrangement information, such as the number of free index nodes, when new files are created.

In resizing, new descriptor blocks have been created to map the file metadata to the actual physical counterpart.

3.2.6 Verifying the added storage space​

After extending and resizing the volumes, we must ensure everything was correctly executed. Run the volume group display to check the current setup:

sudo vgdisplay

The output should be something like this:

  --- Volume group ---
  VG Name               ubuntu-vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               [VOLUME_GROUP_SIZE]
  PE Size               4.00 MiB
  Total PE              [TOTAL_PE]
  Alloc PE / Size       [ALLOCATED_PE] / [FULL_DISK_SPACE]
  Free  PE / Size       0 / 0
  VG UUID               [UNIVERSALLY_UNIQUE_IDENTIFIER]

During the checkup, look out for the following values:

  • [VOLUME_GROUP_SIZE] should be equal to [FULL_DISK_SPACE]
  • [ALLOCATED_PE] should be equal to [TOTAL_PE]
  • Free PE / Size should be 0 / 0

We can also recheck the disk usage:

df -h

The storage mounted on / should've increased. The percentage usage should have been decreased depending on how much storage you added. Keep in mind your numbers will be different:

Filesystem                         Size  Used Avail Use% Mounted on
tmpfs                              3.2G  1.6M  3.2G   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv  1.8T   11G  1.8T   1% /
tmpfs                               16G     0   16G   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
/dev/nvme0n1p2                     2.0G  131M  1.7G   8% /boot
/dev/nvme0n1p1                     1.1G  6.1M  1.1G   1% /boot/efi
tmpfs                              3.2G  4.0K  3.2G   1% /run/user/1000

If the logical storage volumes are extended correctly, we can continue configuring our software updates.