Mirrored Operating System

[Brian Fassett]

We have parched 2.0 hard drive to be used as a backup to our operating system.
We would like to mirror the operating system on a set schedule and configure
the new drive so that it could be use as the bootable drive in the event of the
primary hard drive crashed (Minimal down Time. Take out the bad drive and use
the good drive).
Not to sure on what the best first step should be. Is there software that can
do this or is it just a manner of configuring the current system to do it?

Any suggestions would be very helpful.

[Terja Lange_1]

Rather than mirror your operating systems occasionally you should mirror it
full time. This way should a
disk fail for instance the primary disk, the machine will continue to operate.
You can then change the disk at yoiur leasure.

In order to full time mirror, you need to have MirrorDISK/UX installed.
mirroring a filesystem is easy

extendfs -l /dev/vg00/0 ....

[Dave Wherry_1]

As Terja said you do need MirrorDISK/UX and it is a chargable product.
However, I don't think you can mirror using extendfs. Maybe you can, I have
not seen that. Use lvextend as the mirroring happens at the logical volume
level.
Also, mirroring the operating system requires more than just mirroring other
file systems. You need to prepare the disk to be a mirrored operating system
and be able to boot from it. There are two documents on the ITRC that explain
it. "Mirroring the Root Volume Group" Id rcfaxlvm001 and "Booting from
mirrored/split environment" Id X1401978 pretty much cover it.
Make sure you test it by booting from the mirror.