What is Logical volume management?
{{jargon|date=January 2024}} '''Logical volume management''' is a method of [[Allocation|allocating]] computer storage. It is about allocating space on ''mass storage devices'', like [[hard drive]]s. It is more flexible than the [[Disk partition|partitioning]] of the drive into static (unchangeable) volumes. With a logical volume manager it is possible to grow partitions, even beyond the size of one physical disk. It is also possible to use striping or to put partitions together and combine them while they are being used. Logical volume management is a form of [[Virtualization|virtualisation]]. It makes it easier to adapt to the changing storage needs of computer users. == Design == Volume managers differ but some basic concepts exist across most versions. The volume manager starts with ''physical volumes'' or PVs, which can be [[hard disk]] [[partition (computing)|partition]]s, [[RAID]] devices or [[Storage area network|SAN]] [[LUN]]s. PVs are split into small chunks of even size (a default of 4 [[megabyte|MB]] on HP-UX) called ''physical extents'' or PEs. The PEs are then pooled into a ''volume group'' or VG. The pooled PEs can then be joined together into virtual disk partitions called ''logical volumes'' or LVs. These LVs behave just like hard disk partitions: mountable [[file system]]s can be created on them, or they can be used as raw [[block device]]s for [[virtual memory|swap]]. The LVs can be grown by joining more PEs from the pool. Some volume managers allow LV shrinking; some allow online resizing in either direction. Changing the size of the LV does not necessarily change the size of a [[file system|filesystem]] on it; it merely changes the size of its containing space. A file system that can be resized online is recommended because it allows the system to adjust its storage [[on-the-fly]] without interrupting [[Application software|applications]]. PVs may also be organized into ''physical volume groups'' or PVGs. This allows LVs to be mirrored by pairing together its PEs with [[Redundan