Re: LVM-Howto [Was : what are the restrictions on bootablepartitions?]

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ow.mun.heng@xxxxxxx wrote:



-----Original Message-----
From: neil [mailto:neilcuk@xxxxxxx]


mr700@xxxxxxxxxxxx wrote:



On Friday 30 April 2004 05:11, Ow Mun Heng wrote:




-----Original Message-----
From: neil [mailto:neilcuk@xxxxxxx]
Sent: Thursday, April 29, 2004 10:35 PM
To: For users of Fedora Core releases
Subject: Re: what are the restrictions on bootable partitions?




rpjday@xxxxxxxxxxxxxx wrote:





what are the restrictions on where i can install another



linux distro




onto my fedora core (actually, FC2-t3) system so that grub



can find it?




(even though this is a test version of fedora, this

question actually


refers to FC distros in general.)






There are no restrictions other than the boot loader (grub) must be able to read the boot partition.





typically, for historical reasons, even when i use LVM, i



create a small




primary, ext3 filesystem for /boot, and use LVM for the rest



of the drive.




is there any compelling reason for doing this anymore?

what's the

recommended strategy for LVM? and need for a non-LVM



filesystem on newer




machines?





It really depends on what the system will be used for.

Check out the

howto here: http://www.tldp.org/HOWTO/LVM-HOWTO/index.html




I've actually looked through the howto but am still unable

to determine


how to actually create a lvm system. I've recompiled my kernel to have the devive mapper as a module and modprobe'ed it.

When I try to do vgscan it states that the kernel modules

are not loaded.






I don't remember how I did this with RH9 to make it

work, but I remember


I played a bit whth modprobe, the LVM tools and the man pages :)




Please help.




http://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/s


ysadmin-guide/ch-lvm.html


http://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/s


ysadmin-guide/ch-lvm-intro.html


http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/custo


m-guide/ch-lvm.html


http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/custo


m-guide/ch-lvm-intro.html


http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/custom-


guide/ch-lvm-intro.html


...
I did install FC1 with Software Raid 5 and LVM on top of


it, but doing so on less


than three physical disks results to up to 5 times slower

transfer (because of the


raid). If you have 3 disks read speed increases and the

write speed is almost the


same. Using ReiserFS I was able to resize 61G LV to 64G LV

without errors. With


ext3 it worked, but fsck.ext3 had a lot of work to do (the

partition was ~50G full).


I hope one day online resize will work with bouth and

reiserfs will get more stable


with acl and SELinux support.
  http://www.aplawrence.com/Linux/lvm.html
  ps: putting the /boot partiton ouside the LVM worked fine for me.





okay - there are a few steps one needs to take to get their system using LVM. It can be tricky to get your brain around at first but it will slot into place. The steps are quite straight forward - even when setting up post install. Here's a brief overview. I'm assuming you can follow the man pages of each of the commands specified - there are a number of options which will be up to you:

as root
One(a): Make sure you have backed up any important data before trashing your system ;-)
One: make sure your kernel supports LVM (By default this is supported in FC1)
Two: create some LVM partitions (of type 8e under fdisk)
Three: reboot or execute partprobe
Four: execute vgscan
Five: use pvcreate to assign your newly typed disks as use within the LVM
(actually, four and five might be back to front)
Six: use vgcreate to generate a new volume group (and add some physical volumes tro it)
Seven: use lvcreate to make your logical volume
Eight: format your new logical volume


then it's up to you - mount as you like

use e2fsadm to extend and reduce the size of the volume

There is a huge amount of documentation and you should really get to grips with resizing, adding new PVs etc. Before you start putting useful data on your new LV!




Thanks for the info Neil. I think I do have a hang of it.. sort of anyway.
So, what you're saying is that I have to create the LVM partition using
fdisk 1st before I can get to execute vgscan??


Currently I just type vgscan and then it complains
vgscan -- LVM driver/module not loaded??

(it's loaded. The module is named dm-mod.ko right??)






you've got me there. It should be 'lvm-mod' that gets loaded. try a manual 'modprobe lvm-mod'. If that works try running 'depmod' to setup the module dependancies again. Sounds like something is missing the mark. Create one or two partitions using fdisk and try vgscan again.

neil



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