Chicken and egg problem with LVM

[plate]

It's either my faulty logic or lack of experience or both or worse: I've just added a second HDD to a stone-age desktop PC to alleviate the pressure on its legacy 1.5 GB drive that didn't have enough space left to emerge X... It's still not impressive, the new 2 GB disk that's now spinning inside that case is actually a leftover from my four year old notebook, and whatever I did, it doesn't make a 166 Mhz MMX and 64 MB RAM look any faster. Anywho, I'd love to span the root partition over both disks now, to which end I've a) compiled LVM support in the kernel and b) emerged the lvm-user apps.

Here's what's baking my noodle: I already have a very nice root partition, /dev/hda3, like I'm s'pposed to. If I pvcreate a physical volume LVM style on an existing partition to add to a volume group now, I'll lose all the data on that partition, says the book. If I create the volume group on /dev/hdb instead, I can't extend it over /dev/hda3 unless I pvcreate it, can I? No chicken, no egg, much less the reverse.

Anybody know a good way out of this? Will I have to move the entire root partition out of the way while I'm redecorating my disk space? Can I do that at all, I mean, what happens to all the devices in that case? I could always break up /dev/hdb into chunks of /var and /usr and /home and mount those individually, but the whole LVM idea is that I wanted to avoid fixed partition sizes.

Really grateful for any idea you might have.

[Cyrix]

As of the LVM documentation it is not recommended to use LVM for the root partition. It is easier and safer to use a fixed root-partition.

I would suggest you to use LVM for other partitions and to use symlinks if you run into space problems.

In order to emerge X you just need to throw /usr and /var/tmp to your LVM partition.
_________________
Wo ein Willis ist, ist auch ein Weg.

[plate]

[Cyrix]

If you really want root on a Logical Volume, you should make a complete backup of your root-system on CD or another Systems HD and consult
http://www.sistina.com/lvm_howtos/lvm_howto/Converting_a_root_filesys.html
(but read the NOTE carefully !)

I'd rather suggest you to make a full backup and rearrange your partitions then.
Use 512 MB for / and the rest under a new partition which can be "put under the LVM umbrella" as you would call it.

I personally fear the complications for system-updates when using lvm for / because the easiness of this task brought me to gentoo and before it to debian...

But in the end the choice is up to you !
_________________
Wo ein Willis ist, ist auch ein Weg.