[KLUG Members] Mirroring disk which is under LVM control

[Adam Tauno Williams]

> We recently acquired Dell rack-optimized server.  The supplied Open
> Manage CD took care of the installation of RHES 4.0.  It simply asked
> for configuration information like disk partitions, network settings,
> etc.
> After the installation, I realized that the LVM is enabled.
> The box comes with two (2) SATA disks and I intend to mirror them for
> added data protection.  My problem is, the first disk is already under
> LVM control.  Would it still be possible to mirror the disk?

I don't think so,  the MD layer exists underneath the LVM layer.  You'd
need a hardware RAID controller to make a non-mirrored volume into a
mirror.

> the server uses Intel ICH7R SATA disk controller and the installation
> kernel does not have the driver preloaded.  I already tried to
> re-install the OS and load the driver by using a driver disk, but
> still, the installation kernel cannot detect the SATA disks, hence the
> installation cannot proceed.

Sorry, I've never installed RHES or worked with SATA drives.  I'm an
old-school SCSI guy all-the-way.

> So I guess my best direction is to try to mirror the first disk.  Is
> there anyway to go around LVM?

No you can't mirror in LVM;  LVM expects something else to take care of
redundancy.  You could attach an external storage device, migrate the
volumes off the internal drives,  create the mirrors, and migrate them
back,  I've done things like this using a 200Gb crap-IDE drive in a USB
enclosure,  a pretty fast way to shove data out of the way so you can
restructure an array.