Disk Recovery - Part II

[dsr at tao.merseine.nu (dsr at tao.merseine.nu)]

On Thu, Dec 15, 2005 at 10:43:22PM -0500, Don Levey wrote:
> OK, so I've just ordered 2 160GB drives, which should be in early next week.
> Here's the plan, though I am probably missing some steps.  The original disk
> is also 160GB, in three partitions: /, /misc, and /home.  The /misc is what
> I've used as a temporary area for backups (mondo/mindi images), so I don't
> really need to keep the data in that area:

Yay backups!

> * Install one disk in my external USB housing.
> * fdisk and format to partition that disk as the previous one.
> * copy data from the old /home (/dev/hda3) partition using dd
> * copy data from old / partition - I suppose I should use dd there too, to
> copy MBR, or can I just use cp -a?

For both of these, I would recommend using rsync rather than dd,
and then reinstalling your boot loader.

> * install second disk in USb enclosure, fdisk/format
> * install both disks in main case (on separate IDE interfaces) and mdadm to
> set up RAID
> * Boot system from new RAID to test.

As always, having a copy of the Software-RAID-HOWTO printed out
will be useful.

> Should mdadm synch up the drives so that the data will be mirrored
> automatically?

Yes, that will take a while. Look at /proc/mdstat to see how
it's going. Don't expect full performance until it's done.

> Should I have a single /boot partition on a non-RAID?  I've heard that
> booting from RAID can be tricky.

Here's my standard layout at work:

size	disk1	disk2	explanation
100MB	/boot	/boot2	rsync'd copy after successful boot
1 GB	swap	swap	2GB swap, Linux adapts for performance
rest	RAID	RAID	/ 

This doesn't hold for specialized servers (mail, disk farms,
databases) but it works very well for desktops, web servers and
most application servers. GRUB is installed twice, once per
disk, with each one knowing about the local /boot partition and
using "kernel /vmlinuz root=/dev/md0"

-dsr-