Bug#515607: partman-auto-lvm: ask how much VG space to use
On Monday 16 February 2009, Colin Watson wrote:
> > The "or if you add more disks" also makes no sense in the context of
> > your patch.
>
> Sure it does; if you add more disks, you can add new physical volumes
> on them and easily extend your volume group. This is pretty standard
> LVM operation.
Yes, it is indeed basic LVM. I just don't see what value mentioning a new
disk adds in this context and it really does not relate at all to the
last part of the sentence ("so using a smaller amount of disk [...]").
I would really just drop the ", or if you add more disks later,".
> > I wonder if it would not be better to allow users to specify to leave
> > a _partition_ of a certain size unused. That would also make it
> > usable for non-LVM guided partitioning and is a much better match for
> > the description in your template.
>
> That would be much less useful. If you're using LVM you generally want
> to just use LVM (with the exception of stuff like a /boot partition or
> / outside LVM or whatever), and generally it's much more convenient to
> just stick all unused disk space into the volume group. That doesn't
> necessarily mean that you want it all to be allocated to logical
> volumes up-front.
One case where that's not true is with encrypted LVM. You might want to
reserve some disk space for use _outside_ the encrypted partition [1].
I don't see why it would be less useful. You'd just create a new PV, add
it to the existing VG and done. Maybe a bit more work, but still basic
LVM. I'd even say more flexible rather than less useful [2].
I actually think it is more useful as it allows users who do not use LVM
to leave part of their hard disk free. Your implementation only works for
LVM.
But maybe we should consider supporting both? Main disadvantage of that is
we'd be adding yet another dialog. Maybe these options should be medium
prio?
Note that I'm not totally opposed to your patch, but you did ask for
comments and I do think we should consider the different use-cases,
options and alternatives.
Cheers,
FJP
P.S. The error dialogs should be displayed at critical prio, so they at
least get displayed in case of wrong preseeding during automated
installs.
[1] I recently found that having disk images for VirtualBox inside my
encrypted LVM causes annoying overhead. I'll now have to shrink FS ->
LV -> VG -> PV -> encrypted partition to create some free space.
[2] Hmmm. For the encrypted LVM case this really is different as you'd
first have to encrypt the partition, and that would mean a second key.
Nasty.
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