LVM on a laptop
Paul Howarth
paul at city-fan.org
Tue Jan 3 13:15:50 UTC 2006
William John Murray wrote:
> Hello all,
> I just faced a laptop problem: How to shrink the FC4
> allocated space in order to increase the space on another operating
> system. I had used the default LVM.
> A trusty knoppix liveCD QTparted knows nothing of LVM, so I tried the
> FC4 rescue. After a long time, I found:
> * resize2fs shrinks the ext3 / area. OK
> * lvm lvreduce shrinks the logical volume (different units)
> * lvm pvmove allows me to put all the lvm handled stuff physically
> together. More different units.
> * vgreduce...fails
>
> I think I was supposed to use vgreduce to shrink the space managed in
> the volume group - but I couldn't make it work. It only seems to delete
> logical volumes.
> Finally I reversed all the above operation. Since they are all in
> different units, and I had padded a little to be safe, I had to pad
> some more on the way back, and now I have wasted space.
>
> Two questions:
> *) How could I have made it work?
There is no straightforward way of shrinking an LVM physical volume that
I know of. I think you need to have some way of shifting all of the data
off that volume to somewhere else (e.g. backups, another disk), delete
the volume and then create a new, smaller one.
> *) What benefit is there in lvm on a laptop, when you pretty much know
> there will only be 1 disk?
In the default configuration of one big physical volume and one logical
volume for the whole system (exceot swap), there's not a lot of benefit.
However, if you configure it manually and use multiple volumes so as to
keep for instance the /, /var, /usr, /tmp, /home filesystems separate,
and/or you don't allocate all available disk space to the physical
volume, then LVM has benefits in that you can reallocate space usefully
later on. Just don't create a physical volume that you may need to
shrink in the future - it's better to create something too small and
then add to it when necessary,
Paul.
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