Mark the Physical Devices as Physical Volumes We will start by walking through a basic procedure that will use two physical disks to form four logical volumes. Now that you are familiar with some of the terminology and structures LVM uses, we can explore some common ways to use LVM. Logical volumes can also be easily expanded or shrunk by simply adding extents to or removing extents from the volume. LVM can copy and reorganize the physical extents that compose a logical volume without any interruption to users. The logical extents that are presented as a unified device by LVM do not have to map to continuous physical extents. Because of this relationship, the extent size represents the smallest amount of space that can be allocated by LVM.Įxtents are behind much of the flexibility and power of LVM. A logical volume is simply a mapping that LVM maintains between logical and physical extents. The extents on a physical volume are called physical extents, while the extents of a logical volume are called logical extents. The size of the extents is determined by the volume group (all volumes within the group conform to the same extent size). What are Extents?Įach volume within a volume group is segmented into small, fixed-size chunks called extents. Afterwards, administrators can segment the volume group into arbitrary logical volumes, which act as flexible partitions. In summary, LVM can be used to combine physical volumes into volume groups to unify the storage space available on a system. Logical volumes are the primary component that users and applications will interact with. Logical volumes are functionally equivalent to partitions on a physical disk, but with much more flexibility. Description: A volume group can be sliced up into any number of logical volumes.(generic LVM utilities might begin with lvm.) Volume groups abstract the characteristics of the underlying devices and function as a unified logical device with combined storage capacity of the component physical volumes. Description: LVM combines physical volumes into storage pools known as volume groups.LVM writes a header to the device to allocate it for management. Physical volumes are regular storage devices. Description: Physical block devices or other disk-like devices (for example, other devices created by device mapper, like RAID arrays) are used by LVM as the raw building material for higher levels of abstraction.The basic layers that LVM uses, starting with the most primitive, are. LVM functions by layering abstractions on top of physical storage devices. LVM Architecture and Terminologyīefore we dive into the actual LVM administrative commands, it is important to have a basic understanding of how LVM organizes storage devices and some of the terminology it employs. In this guide, we will briefly discuss how LVM works and then demonstrate the basic commands needed to get up and running quickly. LVM also offers advanced features like snapshotting, striping, and mirroring. Volumes can be resized dynamically as space requirements change and migrated between physical devices within the pool on a running system or exported easily. Logical volumes can have meaningful names like “databases” or “root-backup”. The main advantages of LVM are increased abstraction, flexibility, and control. Utilizing the device mapper Linux kernel framework, the current iteration, LVM2, can be used to gather existing storage devices into groups and allocate logical units from the combined space as needed. LVM, or Logical Volume Management, is a storage device management technology that gives users the power to pool and abstract the physical layout of component storage devices for easier and flexible administration.
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