software raid
Bruno Wolff III
bruno at wolff.to
Tue Nov 7 21:15:03 UTC 2006
On Tue, Nov 07, 2006 at 12:52:35 -0500,
Jeffrey Ross <jeff at bubble.org> wrote:
> I'm looking for a howto guide that will allow me to convert my currently
> running system (FC6) from a non RAID system to a RAID-1 (mirror) system
> using IDE driver (hda and hdc) without loosing the existing data on the
> system.
>
> Current partition table is:
>
> Filesystem 1K-blocks Used Available Use% Mounted on
> /dev/hda6 2972236 280372 2538448 10% /
> /dev/hda1 505604 14881 464619 4% /boot
> tmpfs 1037684 0 1037684 0% /dev/shm
> /dev/hda7 58449748 10858968 44573776 20% /home
> /dev/hda2 5944440 2073532 3564068 37% /usr
> /dev/hda5 3765832 337868 3233580 10% /var
>
> swap is on /dev/hda3
The software raid partition uses a bit of space at the end of a partition
to keep information about the array. So you will need to shrink the file
systems slightly.
If the two drives are the same size, I would suggest coping over the partition
table from hda to hdc and then change all of the partitions on hdc to
software raid (fd). If you reboot at that point the OS will see the
partitions. Then you can create a raid 1 partition with one member for
each partition. You will need to use the force option to do this. Then
you can create the appropiate file system on each partition. (This might
be mkfs.ext3 for ext3 and mkswap for swap.) Then you need to copy over
the files from the old partitions to the new ones. Probably copying the
file systems over is best done with a live CD. You can copy over each
file system from the hda partition to the corresponding md arrays.
You can then unmount the hda partitions and add the corresponding hda
partitions to the md arrays. You will also need to grow the md devices
so that both drives are used (when you first add a new partition to an
md array it will be a spare). Once the arrays are all synced you should
be able to reboot, thought you might want to install grub on hdc as well,
so that if hda fails you can boot off of hdc. Usually what I do for that
is have grub.conf set up to use an hd0 partition and then do
root (hd1)
setup (hd1)
to install the stage 2 stuff on the hdc MBR.
Then
root (hd0)
setup (hd1)
setup (hd0)
to have both MBRs use the first drive to boot. This way if hdc becomes the
first drive you can boot off of it.
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