Logical Volumes: The LVM utility prefix for logical volumes is lv…, generic LVM utilities might begin with lvm…. A volume group can be sliced up into any number of logical volumes. Logical volumes are functionally equivalent to partitions on a physical disk, but with much more flexibility. Logical volumes are the primary component that users and applications will interact with.<\/li>\n<\/ul>\nLVM serves the purpose of merging physical volumes into volume groups, allowing the consolidation of storage space on a system. Administrators can then divide the volume group into any desired logical volumes, which function as adaptable partitions.<\/p>\n
Comprehending the Scope<\/h3>\n
All partitions within a group of partitions are divided into small, consistent-sized portions referred to as extents, which are set by the volume group. Every partition within the group follows the same extent size.<\/p>\n
Physical extents are referred to as extents on a physical volume, and logical extents are the extents on a logical volume. LVM establishes a mapping between logical and physical extents, which defines a logical volume. Consequently, the extent size denotes the minimum space that LVM can allocate.<\/p>\n
LVM’s flexibility and power are largely attributed to extents. LVM combines logical extents to create a single device, and these logical extents are not required to correspond to continuous physical extents. LVM has the ability to copy and rearrange the physical extents of a logical volume without causing any disruption to users. Additionally, the size of logical volumes can be increased or decreased by adding or removing extents.<\/p>\n
Typical scenarios where something is frequently used<\/h2>\n
Once you have become acquainted with the terminology and structures employed by LVM, you can delve into the various ways it is commonly utilized. Commencing with a step-by-step process, you will employ two physical disks in order to create four logical volumes.<\/p>\n
Labeling the physical devices as physical volumes.<\/h3>\n
Start by conducting a scan of the system to identify block devices that LVM can access and control. This can be accomplished by executing the following command:<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> lvmdiskscan<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\nThe result will display a list of block devices that LVM can interact with.<\/p>\n
<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\n\/dev\/ram0 [ 64.00 MiB] \/dev\/sda [ 200.00 GiB] <\/mark> \/dev\/ram1 [ 64.00 MiB] . . . \/dev\/ram15 [ 64.00 MiB] \/dev\/sdb [ 100.00 GiB] <\/mark> 2 disks<\/mark> 17 partitions 0 LVM physical volume whole disks 0 LVM physical volumes<\/p>\n<\/code><\/pre>\nIn this particular case, it is important to observe that there are presently two disks and a total of 17 partitions. These partitions primarily consist of \/dev\/ram* partitions, deployed in the system as RAM disks to optimize performance. The disks in this instance are \/dev\/sda, encompassing 200G of storage, and \/dev\/sdb, having a capacity of 100G.<\/p>\n
\n
Warning<\/p>\n
Please ensure to verify that the devices you plan to use with LVM do not contain any crucial data. Utilizing these devices with LVM will replace the existing content. It is advisable to create backups of any significant data on your server before proceeding.<\/div>\n<\/div>\n
After identifying the specific physical devices you intend to utilize, designate them as physical volumes within LVM by employing the pvcreate command.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> pvcreate \/dev\/sda<\/mark> \/dev\/sdb<\/mark><\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nPhysical volume “\/dev\/sda” successfully created Physical volume “\/dev\/sdb” successfully created<\/p>\n
<\/code><\/pre>\nThis action involves creating an LVM header on the devices, indicating their readiness for addition to a volume group.<\/p>\n
To confirm the registration of physical volumes in LVM, execute the command “pvs” and ensure their presence.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> pvs<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nPV VG Fmt Attr PSize PFree \/dev\/sda lvm2 — 200.00g 200.00g \/dev\/sdb lvm2 — 100.00g 100.00g<\/p>\n
<\/code><\/pre>\nPlease observe that both of the devices can be found in the PV column, which represents physical volume.<\/p>\n
Including the Physical Disks in a Volume Group<\/h3>\n
After you have successfully generated physical volumes from your devices, you are able to form a volume group. It is recommended to have only one volume group per system to achieve optimal flexibility in allocation. The given instance of a volume group is denoted as LVMVolGroup, but feel free to choose any name for your own volume group.<\/p>\n
To establish the volume group and incorporate both of your physical volumes, execute the following command:<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> vgcreate LVMVolGroup<\/mark> \/dev\/sda<\/mark> \/dev\/sdb<\/mark><\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nVolume group “LVMVolGroup” successfully created<\/p>\n
<\/code><\/pre>\nUpon reviewing the pvs output once more, you will observe that your physical volumes are now linked to the new volume group.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> pvs<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nPV VG Fmt Attr PSize PFree \/dev\/sda LVMVolGroup<\/mark> lvm2 a– 200.00g 200.00g \/dev\/sdb LVMVolGroup<\/mark> lvm2 a– 100.00g 100.00g<\/p>\n<\/code><\/pre>\nProvide a brief overview of the volume group by using the command “vgs.”<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> vgs<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nVG #PV #LV #SN Attr VSize VFree LVMVolGroup 2 0 0 wz–n- 299.99g 299.99g<\/p>\n
<\/code><\/pre>\nAt present, you have two physical volumes in your volume group, with no logical volumes, and the total capacity is the sum of the underlying devices.<\/p>\n
Generating Logical Volumes from the Pool of Volume Groups.<\/h3>\n
Once a volume group is accessible, you can utilize it as a pool to assign logical volumes. In contrast to traditional partitioning, LVM takes care of mapping and managing the volume layout, so you don’t have to worry about it. All you have to provide is the volume size and a name.<\/p>\n
You will divide your volume group into four distinct logical volumes in the upcoming example.<\/p>\n
\n- 10G \u201cprojects\u201d volume<\/li>\n
- 5G \u201cwww\u201d volume for web content<\/li>\n
- 20G \u201cdb\u201d volume for a database<\/li>\n
- \u201cworkspace\u201d volume that will fill the remaining space<\/li>\n<\/ul>\n
In order to generate logical volumes, employ the lvcreate command. It is mandatory to provide the volume group to extract from and the logical volume can be designated using the -n option. To specify the size explicitly, utilize the -L option. Conversely, if you prefer to specify the size based on the number of extents, employ the -l option.<\/p>\n
Use the -L option to establish the initial three logical volumes.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> lvcreate -L<\/span> 10G -n<\/span> projects LVMVolGroup<\/li>\n
- sudo<\/span> lvcreate -L<\/span> 5G -n<\/span> www LVMVolGroup<\/li>\n
- sudo<\/span> lvcreate -L<\/span> 20G -n<\/span> db LVMVolGroup<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nLogical volume “projects” created. Logical volume “www” created. Logical volume “db” created.<\/p>\n
<\/code><\/pre>\nBy opting for a custom output from the vgs command, you have the ability to observe the logical volumes and their correlation with the volume group.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> vgs -o<\/span> +lv_size,lv_name<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nVG #PV #LV #SN Attr VSize VFree LSize LV LVMVolGroup 2 3 0 wz–n- 299.99g 264.99g 10.00g projects LVMVolGroup 2 3 0 wz–n- 299.99g 264.99g 5.00g www LVMVolGroup 2 3 0 wz–n- 299.99g 264.99g 20.00g db<\/p>\n
<\/code><\/pre>\nIn this specific case, you summed up the final two columns of the output, revealing the amount of allocated space for your logical volumes.<\/p>\n
You now have the option to allocate the remaining space in the volume group to the “workspace” volume by using the -l flag, which functions in extents. Another way to specify your intentions more clearly is by providing a percentage and a unit. In this particular scenario, you can allocate the available free space by passing in 100%FREE.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> lvcreate -l<\/span> 100<\/span>%FREE -n<\/span> workspace LVMVolGroup<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nLogical volume “workspace” created.<\/p>\n
<\/code><\/pre>\nWhen you use the custom vgs command to inspect the volume group information, you will observe that all of the available space has been utilized.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> vgs -o<\/span> +lv_size,lv_name<\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\n<\/code><\/pre>\nOutput<\/div>\n
<\/code><\/pre>\nVG #PV #LV #SN Attr VSize VFree LSize LV LVMVolGroup 2 4 0 wz–n- 299.99g 0<\/mark> 10.00g projects LVMVolGroup 2 4 0 wz–n- 299.99g 0<\/mark> 5.00g www LVMVolGroup 2 4 0 wz–n- 299.99g 0<\/mark> 20.00g db LVMVolGroup 2 4 0 wz–n- 299.99g 0<\/mark> 264.99g<\/mark> workspace<\/p>\n<\/code><\/pre>\nThe workspace volume has been successfully established and the entire LVMVolGroup volume group has been assigned.<\/p>\n
The process of configuring and preparing the logical volumes for use.<\/h3>\n
Once you have logical volumes, you can utilize them as regular block devices.<\/p>\n
You can find the logical devices in the \/dev directory, just like other storage devices. These devices can be accessed in two different locations.<\/p>\n
\n- \/dev\/volume_group_name\/logical_volume_name<\/li>\n
- \/dev\/mapper\/volume_group_name-logical_volume_name<\/li>\n<\/ul>\n
To format your four logical volumes using the Ext4 filesystem, execute these commands:<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> mkfs.ext4 \/dev\/LVMVolGroup<\/mark>\/projects<\/mark><\/li>\n
- sudo<\/span> mkfs.ext4 \/dev\/LVMVolGroup<\/mark>\/www<\/mark><\/li>\n
- sudo<\/span> mkfs.ext4 \/dev\/LVMVolGroup<\/mark>\/db<\/mark><\/li>\n
- sudo<\/span> mkfs.ext4 \/dev\/LVMVolGroup<\/mark>\/workspace<\/mark><\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\nYou also have the option to execute the following:<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span> mkfs.ext4 \/dev\/mapper\/LVMVolGroup<\/mark>–projects<\/mark><\/li>\n
- sudo<\/span> mkfs.ext4 \/dev\/mapper\/LVMVolGroup<\/mark>–www<\/mark><\/li>\n
- sudo<\/span> mkfs.ext4 \/dev\/mapper\/LVMVolGroup<\/mark>–db<\/mark><\/li>\n
- sudo<\/span> mkfs.ext4 \/dev\/mapper\/LVMVolGroup<\/mark>–workspace<\/mark><\/li>\n<\/ol>\n
<\/code><\/pre>\n <\/p>\n
<\/code><\/pre>\nOnce you have formatted the device, proceed to establish the designated mount points.<\/p>\n
<\/code><\/pre>\n\n- sudo<\/span>