Booting - Enterprise Volume Management System

[Thiers Botelho]

Thnx Alex, please read below.

On 8/12/06, Alexander Skwar <listen at alexander.skwar.name> wrote:
> · Thiers Botelho <thiersb at gmail.com>:
>
> > On 8/11/06, Alexander Skwar <listen at alexander.skwar.name> wrote:
> >>
> >> Yes, it has. It cannot be used for filesystems on a "dual" boot
> >> system which should be used for data exchange, as LVM can ONLY
> >> be used with Linux. No other OS can read Linux LVM.

Seems that your statement above won't remain true for very long. I
just found http://www.chrysocome.net/virtualvolumes , which while
still in beta will soon be able to do "Reads and Writes LVM2" on
Windoze.

> >> Alexander Skwar
> >
> > Based on your statement above, I'd like to know if the following is
> > feasible (and well, if it makes sense of course):
> >
> > - A triple-boot system with WinXP, Ubuntu and, say, Fedora 5 ;
> >
> > - One primary partition for windoze C: drive and one extended
> > partition to accomodate all the rest ;
> >
> > - one [or more] VFAT logical partitions for data exchange among the 3
> > systems (I know, no data security at all here) ;
>
> Because of that, I'd recommend ext2. There are drivers for Windows,
> which allow accessing ext2 from Windows.

Thnx for the update. I knew previously about
http://www.chrysocome.net/explore2fs which only _reads_ ext* FSes, but
its younger brother virtualvolumes will also be able to do "Reads and
Writes EXT2/EXT3".

Also found http://www.fs-driver.org/ (ext2ifs for Win) which already
does ext* R/W.

However, their FAQ states:
"Access rights are not maintained. All users can access all the
directories and files of an Ext2 volume. "
Therefore I see no real advantage in following your recommendation
(i.e., ext2 for data exchange instead of vfat). Did I miss something ?

>
> > - one (maybe two ?) /boot logical partitions for the Linuxen ;
>
> I'd suggest two - one for every Linux OS. I'd make them ext2.
>

Good.

> > - a fair number of logical partitions, interspersed with some empty
> > chunks of space, to be used under LVM on Ubuntu and FC5.
>
> Uhm - why that? Why a fair number of logical partitions and
> why interspersed with chunks of space? What do you expect
> to gain by that?

Well, looks I was speculating without really understanding some LVM
features. More on that follows below.

>
> If you're going to use LVM, I'd rather make one huge logical
> or primary partition. I'd then make this partition a Physical
> Volume (PV) and create *ONE* Volume Group (VG) which consists
> of just one PV. Next, I'd create as many Logical Volumes as
> needed for Ubuntu and FC5 .
>

OK, I got it (it seems). If I can create many Logical Volumes using
one VG and one PV, and if this one PV is also one huge logical or
primary partition, that gives me the flexibility I'd like for future
messing around with re-placement and re-sizing of filesystems.

The real nicety of this arrangement would be the co-existence of
traditional partitions (for Windows system drive + /boot(s) + data
exchange) and LVM volumes for Linuxen.

I suppose that /swap can be under LVM too, right ?

> Ie. I'd use the SAME VG with Ubuntu and FC5.
>

Makes sense.

> Hm - actually, I'd make the PV a primary partition, so that
> Windows has problems accessing the partition.

Now I'm not thoroughly convinced of this. My understanding is that
Windows can freely access any number of primary partitions. The access
restrictions, as I understand them, would come from types of
filesystems rather than partition types.

I might be wrong on this one, though. My present system boots from a
FAT32 primary partition where Win98 is installed, but the system drive
for WinXP is really a logical partition so I can't claim to have
access to 2 primary partitions. But I'm _almost_ certain - from a
3-year-ago memory - that I had a slightly different setup on my old
office machine, where Win98 and Win2K were on 2 different _primary_
partitions and both of them were visible to 2K. Unfortunately that box
is now history, so I can't really confirm that claim anymore.

One problem I see with making the PV a primary partition would be,
since all primary partitions come _before_ the logical partitions, a
reduced flexibility in administering filesystem sizes. See, if the PV
is a _huge_ primary partition, and coming before all the logical
partitions, the logical partitions for two /boot's plus the ones for
the data exchange would all have to be squeezed against the end
boundary of the disk. I surely wouldn't want that - some loss of
flexibility in administering space and increased seek times for many
processes.

> As we don't
> even want Windows to access this partition, that's fine. The
> data exchange partition, I'd make a logical partition.
>

See my comments above.

> Alexander Skwar

Cheers

Thiers