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Linux.org.mt: LVM can eliminate hard disk headaches

Sep 09, 2001, 11:44 (19 Talkback[s])
(Other stories by Ramon Casha)

[ Thanks to Ramon Casha for this link. ]

"The ideal situation would be if hard disk storage were added and removed more or less like RAM: you simply add a new disk to your "hard disk pool" and get "x" megabytes of additional space on your filesystem. The space gets added to your existing directory tree instead of requiring you to create a new mount point and mount the new hard disk there.

In Linux, this is the job of the Logical Volume Manager. With the LVM, you no longer have to worry about how much space each partition will contain. In fact, you may no longer have to worry about partitions at all. Instead of partitions and hard disks, you have logical volumes. Here are some of the possibilities offered by the LVM:

  • You don't need to accurately calculate beforehand how much space each partition/LV will need. Space allocation can be altered afterwards.
  • Several physical disks or partitions can be treated as a single large drive.
  • It is possible to add or remove disks from the logical volume. You can remove a failing disk and replace it with a new one - or replace a slow disk with a fast one. Data will be moved off the disk that is going to be removed onto the ones that will remain.
  • You can resize logical volumes easily, and can transfer free space from one LV to another.
  • You can create a "snapshot" of a logical volume for hot backups. This allows you to take consistent backups without stopping anyone. The backup will contain the state of the disks at the time the snapshot was started - no matter how long the backup takes.

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