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Re: [linux-lvm] Query regarding conversion of root partition to LV



Hello Prateek !
You need 3 PV to use LVM mirroring.
You can't boot using Grub on an LVM so I advised of a plain partition with an EXT2/3 FS to hold the kernel and grub setup files. I doubt you can plug and have the disk recognized/discovered without turning the machine down. But your mileage may vary. Last but not least, having the same partition scheme on the two disks will help maintain the system in the future. Bear in mind that in order to use the remaining space on the original disk, you've to play with the partition table and that the kernel will/may fool you because it *has* to know the exact partition used because the root filesystem relies upon it.
Hope this helps.
Prateek Donni a écrit :
Hey George,
     I am trying to make use of LVM's existing mirroring feature to
protect data from disk failures.
So i want to convert the original root into an LV.
I thought of making a block device with the free space(as in which is
allocated inside as root )  and create a PV of the same. can this help
? then on the second disk which may have unallocated space, i create
another PV and mirror a volume across it using LVM features.
I dont want to make use of RAID and i have to have my application run
w/o a reboot.

Any suggestions which you can give me considering the above constraints ....


Thanks Prateek



On Wed, Feb 4, 2009 at 7:53 PM, Georges Giralt <georges giralt free fr> wrote:
Prateek Donni a écrit :
I have a fedora 9 installation with two partitions swap and /
partition. Now i want to mirror the files on the root partition to
another disk using LVM mirroring. Since i dint make root on a LV and
have no allocated space left so i am thinking of using the free space
on the root partition as a block device that can be converted into PV
and then mirrored after making it a LV.
Is this feasible?
Can someone let me know wht can be done?

Thanks
Prateek

Hi Prateek !
IMHO this won't work.
As you spoke about mirroring, you can do this :
1) add another disk to the system (ideally same size of the original one)
2) partition it as :
       part #1 used as /boot (about a 100 MB, Ext2/3 FS )
       part #2 the remaining of the disk tagged as LVM.
3) boot your system under Fedora 9 and using LVM mamger create a PV ont the
second partition, then a VG on the PV and then as much LV as you need. Do
not forget to create the swap LV.
4) Format and temporary mount each LV ont the filesystem, recreating the
correct layout but under, say, /mnt.
5) copy the data using a command like : cd / && tar cf - . |(cd /mnt && tar
xf -)
6) under the /mnt layout correct the Grub menu file, then using this as the
root with chroot, re-run grub-install.
7) boot under the new disk and test your system.
If fine,
8) create the same partition layout on the old disk as the new one and
create 2 software raid 1 (mirror) using mdadm, one for the first partition
used as /boot , the other one for the PV.
9) synchronize the md.
Enjoy.
Be carefull and read the man pages before proceding. A complete backup may
prove usefull, also.
Hope this helps.

--
If the only tool you have is a hammer, you tend to see every problem as a
nail.
               Abraham Maslow
A British variant :
Any tool can serve as a hammer but a screwdriver makes the best chisel.

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_______________________________________________
linux-lvm mailing list
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https://www.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/




--
If the only tool you have is a hammer, you tend to see every problem as a nail.
                Abraham Maslow


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