Re: [linux-lvm] lvm on a single big partition or just a single big partition?

[Marian Csontos <mcsontos redhat com>]

Zhengquan Zhang wrote:
> On Wed, Jun 03, 2009 at 02:42:29PM -0400, Stuart D. Gathman wrote:
>   
> > On Wed, 3 Jun 2009, Zhengquan Zhang wrote:
> >
> >     
> > > For one harddrive I often create a /boot parition that is not lvm and
> > > create a huge partition on the rest of the harddrive for PV of lvm. Now
> > > I am thinking what is the difference between doing partition like this
> > > and just a single big partition without lvm?
> > >       
> > With LVM, you can create many logical volumes.  If you only ever create one
> > logical volume that fills the entire PV, and you aren't spanning drives
> > (multiple PVs) or mirroring, then LVM is not doing anything for you.
> >     
Not at the moment, but the moment you run out of space and decide to add 
another drive, it will save you a lot of trouble moving all your 
partitions around...
> That is what I am doing, so I am not fully utilizing lvm. another
> question, is it advisable to create on pv for one harddrive? 
>
>   
Yes, it is the right way. Having 2 PVs on single drive offer no benefit 
I can think of, and actually it is a step back - you can not share "free 
space" between PVs, thus it is a way to simulate old fashioned partitions.
> > Even with just one LV, leave some space for a snapshot.  Then you can
> > take more consistent backups by creating a snapshot of your main LV
> > and backing that up instead.  Put your swap space in LVM as well.
> >     
>
> Thanks for pointing out this. I never thought of leaving space for
> snapshot. and the swap too, why it is good to put swap in lvm?
>
>   
I think most of installers do not think of it neither (unless you 
partition you disk yourself, which is not so difficult, but may be a bit 
scary for newbies) - I would like an install option "leave N% of created 
PV free and use only the rest now".
> > One reason to create multiple LVs is for virtual machines.  If you
> > run Xen, VMWare, or other virtual machine, then each virtual machine
> > should have its own LVs for disk drives.  This is more efficient
> > than using a filesystem file for a virtual disk.
> >     
>
> Oh really, I never thought about this, so virtual machine can directly
> use lv for the as their filesystem?
>
>   
> > PS.  I wonder if Grub will ever support LVM?  Does LILO work with LVM?
> >     
>
> As I know, LILO does, buy anyway we've got separate /boot.
>
> Thanks a lot Stuart, it helped me a lot,
>
>