LVM ?

LVM is a logical volume manager for the Linux kernel, it manages disk drives and similar mass-storage devices. The term "volume" refers to a disk drive or partitions.


LVM is suitable for:

• Managing large hard disk farms by letting you add disks, replace disks, copy and share contents from one disk to another without disrupting service (hot swapping).
• On small systems (like a desktop at home), instead of having to estimate at installation time how big a partition might need to be in the future, LVM allows you to resize your disk partitions easily as needed.
• Making backups by taking "snapshots."
• Creating single logical volumes of multiple physical volumes or entire hard disks, allowing for dynamic volume resizing.

One can think of LVM as a thin software layer on top of the hard disks and partitions, which creates an illusion of continuity and ease-of-use for managing hard-drive replacement, repartitioning, and backup.


Features of LVM:

• Resize volume groups online by absorbing new physical volumes (PV) or ejecting existing ones.
• Resize logical volumes (LV) online by concatenating extents onto them or truncating extents from them.
• Create read-only snapshots of logical volumes (LVM1).
• Create read-write snapshots of logical volumes (LVM2).
• Stripe whole or parts of logical volumes across multiple PV.
• Move online logical volumes between PVs.
• Split or merge volume groups. This can be useful when migrating whole logical volumes to or from offline storage.