Linux LVM

Courtesy:  Wikipedia

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 (somewhat similar to RAID 0, but more similar to JBOD), 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

The LVM can:

  • 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 PVs, in a fashion similar to RAID 0.
  • Mirror whole or parts of logical volumes, in a fashion similar to RAID 1.
  • Move online logical volumes between PVs.
  • Split or merge volume groups in situ (as long as no logical volumes span the split). This can be useful when migrating whole logical volumes to or from offline storage.

The LVM will also work in a shared-storage cluster (where disks holding the PVs are shared between multiple host computers), but requires an additional daemon to propagate state changes between cluster nodes.

LVM does not:

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