Sunday, May 6, 2012

LVM logical volume manager

This post raised my interest in knowing more about LVM.

The whole concept of partitioning is changed to another level, with different keywords and rules. What is important of LVM is its flexibility that it provides to the user.

From the Arch Wiki:
With LVM you can more easily handle your partitions (logical volumes) than normal hard drive partitions. For example, you can:
  • Use any number of disks as one big disk(VG)
  • Have partitions(LV) stretched over several disks (they can be as big as all of your disk storage together)
  • Resize/create/delete partitions(LV) and disks(VG) as you like (it does not depend on position of the logical volumes within volume groups as with normal partitions)
  • Resize/create/delete partitions(LV) and disks(VG) online (filesystems on them still need to be resized, but some support online resizing)
  • Name your disks(VG) and partitions(LV) as you like
  • Create small partitions(LV) and resize them "dynamically" as they get more filled (growing must be still done by hand, but you can do it online with some filesystems)
So this is a very interesting offering.
Also taking snapshots of your system can be done in a much more space efficient way. The obvious disadvantage that it makes things more complex. If you want grub legacy you need to make a separate /boot partition as it cannot read from LVM volumes. And:
When choosing mountpoints, just select your newly created logical volumes (use: /dev/mapper/Volgroup00-lvolhome).
Do NOT select the actual partitions on which logical volumes were created (do not use: /dev/sda2). 
Details on the necessary configuration you can read on the wiki page. But it is definitely good to know what LVM has to offer because it offers solutions in all kind of situations and scenarios.

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SteveBrad said...
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