[vox-tech] LVM fun

[Samuel Merritt]

--9v2bTOXBzuB5Piju
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Wed, May 15, 2002 at 04:06:37PM -0400, msimons@moria.simons-clan.com wro=
te:
> On Wed, May 15, 2002 at 01:01:14PM -0700, Samuel Merritt wrote:
> > On Wed, May 15, 2002 at 01:49:13PM -0400, msimons@moria.simons-clan.com=
 wrote:
> > > Is anyone using LVM here?
> >=20
> > I use LVM. Kernel 2.4.17, LVM version 1.0.1-rc4(ish)(03/10/2001).=20
>=20
> Hi Sam,
>=20
>   I was digging around in ext2resize man pages, and noticed a lot of=20
> references to LVM, I'd also heard something about LVM hitting a 1.0
> status.  So I got curious about it... I haven't looked around for
> information yet...
>=20
> - What sources of information on LVM would you recommend?

Pretty much everything I needed to do was in the HOWTO, at=20
http://www.sistina.com/lvm_howtos/lvm_howto/ .=20

If you use Debian stable, you'll want bunk's packages for kernel 2.4,=20
which include up-to-date LVM packages. I've got the following in=20
/etc/apt/sources.list:=20

deb http://www.fs.tum.de/~bunk/debian potato main=20

I recently upgraded the machine to woody, and woody has a slightly newer=20
lvm package.=20
=20
> - Is there much of a performance hit on LVM'd versus non-LVM'd filesystem=
s?

I started using LVM when I got three new drives and put them in a RAID-5,=
=20
so I can't really say.=20

If you're interested, my configuration is as follows:=20
/dev/hdc1, /dev/hdf1, /dev/hdg1 make up /dev/md0, which is a RAID-5 array.=
=20

/dev/md0 is the only physical volume in volume group "raid" (uber-creative=
=20
name)

Volume group "raid" has two logical volumes on it:=20
/dev/raid/usr, 4 GB.=20
/dev/raid/home, 130 GB.=20

There's about 10 GB free on the RAID-5 for future expansion. I've been=20
meaning to move /var onto it so I don't lose my mail spool if /dev/hde=20
goes out (has /, /var, and windows (boo, hiss)), but I just haven't gotten=
=20
around to it.=20

> - Do you think things are stable enough for everyday use?

The only problem I had with LVM is that you couldn't mount a snapshot of=20
an ext3 filesystem. There's a patch for that available at=20
http://lists.sistina.com/pipermail/lvm-devel/2001-November/000707.html

I think one piece of the patch has been integrated into 2.4.17, so if one=
=20
hunk fails, that's okay. I looked at the original kernel source; the=20
relevant bits are in there.

Hopefully, all the patch will make it into the 2.4 tree someday.

> - Do you think distributions will start installing LVM'd filesystems?

I don't know. It'd certainly be nice if they did. If you need more space
on /home, it's very nice to be able to buy another disk and do the
appropriate magic to add the new disk in. Had 10G on /home, bought a 40G
disk? Now /home is 50G, no messing about with copying a filesystem or
leaving unused partitions around.=20

It's a nice abstraction -- you can just consider your total disk space,
instead of having to worry about how much space is on each disk.=20

The only problem I see is needing the kernel to be on a regular partition=
=20
in order for LILO or GRUB to work. Otherwise, the bootloader would have to=
=20
scan all the devices, find the LVM info blocks, find the kernel file, and=
=20
load it. And that only works if the BIOS can even see all the block=20
devices used - in my case, that would mean LILO would need to know about=20
LVM and RAID-5, and be able to still fit in the MBR.=20

--=20
Samuel Merritt
PGP key is at http://wwwcsif.cs.ucdavis.edu/~merritt/snmerritt.asc
Information about PGP can be found at http://www.mindspring.com/~aegreene/p=
gp/

--9v2bTOXBzuB5Piju
Content-Type: application/pgp-signature
Content-Disposition: inline

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see http://www.gnupg.org

iD8DBQE84s5Ha6Tf6HA+Z6IRAuErAJ9W/tGCy3b6oTpWj/fmifA5h4cenQCfQfBv
R1EYSKHarQNdP3kljvSPHvE=
=UEh2
-----END PGP SIGNATURE-----

--9v2bTOXBzuB5Piju--