Managing Logical Volumes On Linux
If you create your filesystems using standard partitions on hard drives, trying to add additional space to an existing filesystem can be somewhat of a painful experience. You can only expand a partition to the extent of the available space on the same physical hard drive. If no more space is available on that hard drive, you’re stuck having to get a larger hard drive and manually moving the existing filesystem to the new drive.
What would come in handy is a way to dynamically add more space to an existing filesystem by just adding a partition from another hard drive to the existing filesystem.
The Linux Logical Volume Manager (LVM) software package allows you to do just that. It provides an easy way for you to manipulate disk space on a Linux system without having to rebuild entire filesystems.
Multiple PV elements are pooled together to create a volume group (VG). The logical volume management system treats the VG like a physical hard drive, but in reality the VG may consist of multiple physical partitions spread across multiple hard drives. The VG provides a platform to create the logical partitions, which actually contain the filesystem.
The final layer in the structure is the logical volume (LV). The LV creates the partition environment for Linux to create a filesystem, acting similar to a physical hard disk partition as far as Linux is concerned. The Linux system treats the LV just like a physical partition. You can format the LV using any one of the standard Linux filesystems and then add it to the Linux virtual directory at a mount point.
The picture below will shows the basic layout of a typical Linux logical volume management environment
The volume group, spans across three separate physical hard drives, which contain five separate physical partitions. Inside the volume group are two separate logical volumes. The Linux system treats each logical volume just like a physical partition. Each logical volume can be formatted as an ext4 filesystem and then mounted to a specific location in the virtual directory.
Notice in Figure that the third physical hard drive has an unused partition. Using logical volume management, you can easily assign this unused partition to the existing volume group at a later time, and then either use it to create a new logical volume or add it to expand one of the existing logical volumes when you need more space.
Likewise, if you add a new hard drive to the system, the local volume management system allows you to add it to the existing volume group, and then create more space for one of the existing logical volumes, or start a new logical volume to be mounted. That’s a much better way of handling expanding filesystems!
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| Managing Logical Volumes On Linux |
What would come in handy is a way to dynamically add more space to an existing filesystem by just adding a partition from another hard drive to the existing filesystem.
The Linux Logical Volume Manager (LVM) software package allows you to do just that. It provides an easy way for you to manipulate disk space on a Linux system without having to rebuild entire filesystems.
Exploring logical volume management layout
The core of logical volume management is how it handles the physical hard drive partitions installed on the system. In the logical volume management world, hard drives are called physical volumes (PV). Each PV maps to a specific physical partition created on a hard drive.Multiple PV elements are pooled together to create a volume group (VG). The logical volume management system treats the VG like a physical hard drive, but in reality the VG may consist of multiple physical partitions spread across multiple hard drives. The VG provides a platform to create the logical partitions, which actually contain the filesystem.
The final layer in the structure is the logical volume (LV). The LV creates the partition environment for Linux to create a filesystem, acting similar to a physical hard disk partition as far as Linux is concerned. The Linux system treats the LV just like a physical partition. You can format the LV using any one of the standard Linux filesystems and then add it to the Linux virtual directory at a mount point.
The picture below will shows the basic layout of a typical Linux logical volume management environment
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| The logical volume management environment |
The volume group, spans across three separate physical hard drives, which contain five separate physical partitions. Inside the volume group are two separate logical volumes. The Linux system treats each logical volume just like a physical partition. Each logical volume can be formatted as an ext4 filesystem and then mounted to a specific location in the virtual directory.
Notice in Figure that the third physical hard drive has an unused partition. Using logical volume management, you can easily assign this unused partition to the existing volume group at a later time, and then either use it to create a new logical volume or add it to expand one of the existing logical volumes when you need more space.
Likewise, if you add a new hard drive to the system, the local volume management system allows you to add it to the existing volume group, and then create more space for one of the existing logical volumes, or start a new logical volume to be mounted. That’s a much better way of handling expanding filesystems!
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