FC5T2 anaconda and LVM

Chris Gordon chris at linux-dr.net
Wed Jan 18 03:50:24 UTC 2006

> Just what are the main advantages to LVM over just a
> plain jane ext2 (3) system? Is there a speed penalty
> if you are not using RAID? Any thoughts would be
> appreciated.... still updating the ole brain ROMs. Ric

LVM gives you more flexibility.  Essentially you take a disk partition
and can then cut it up into logical volumes which you then place normal
file systems on.  This can allow you to expand, create and remove
filesystems without having to touch the the disk partition table or
worry about the location space on the physical disk.

Consider this situation.  You have a disk with three partitions:  hda1,
hda2, and hda3.  You've sized them and created file systems as based on
your best initial plans.  As times moves along, you end up no longer
needed hda1 -- whatever the function of it was is no longer a
requirement/need for your system.  During the same time, though, you've
filled up hda3.  In this situation, if you want to recover the space for
hda1 and "add" it to hda3, you've got a good bit of work to do in moving
hda2 around.  Not a pleasant situation.

With LVM, you would have made all of hda into a single PV and then a
single VG.  Within that VG you could have created 3 LVs (logical
volumes) and put the filesystems on them.  Then when you no longer
needed stuff in the first file system, just unmount it and destroy that
LV.  Then you could expand the third LV and grow the filesystem on it
(even can do it all online now without ever taking the box down).

In the traditional volume example, hda2 sits in the middle of the space
you want to use and makes things rather difficult.  With a volume
manager, the exact placement of things on the physical volume is
abstracted and there is no issue.  The ability to easily work with the
volumes is also a plus.

Hope that helped.


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