[clug] Re: [H-GEN] fedora and mylex dac960 raid controller

[Stuart Longland]

Mick Howe wrote:

> I have just obtained a Mylex DAC960PD raid controller that I was 
> intending to use as a simple multi channel scsi controller. It appears 
> that isn't an option, so I need to set it up the way it wants but I 
> don't know how.

Okay, I recently did this with Gentoo Linux, moving a machine from 
software RAID (on Symbios onboard SCSI) across to a similar card.  I 
found it was rather painless (apart from the onboard SCSI playing up -- 
the motherboard got partially sizzled in the recent summer heat, it has 
since been replaced).

Assuming you have your Linux install working just nicely...
1. Recompile your kernel to include dac960 support.  (Under Block 
Devices, not SCSI Low Level Drivers)
2. Make a full backup of your system (I notice you've got a tape drive 
there).  I'd suggest using tar... something basic.
3. Plug the hard drives into the Mylex controller.  Then get ready to 
hit ALT-R at boot.  You should be able to configure the drives to suit 
your needs.  (The BIOS isn't hard -- I managed to do it without docs :-D)

Note that the RAID arrays function like a virtual disk, rather than a 
partition like they do in Software RAID.

4. Boot up a Knoppix disc (You might be able to use the rescue mode of 
Fedora, not sure...).
5. Format the RAID sets as needed, mount the new RAID sets, then start 
restoring your system from the backups.
6. Edit your /etc/fstab to suit.  Also, keep the tapes in a safe place.

As for the device naming... If you're using devfs, it'll be something 
like /dev/rd/c0d0/partN (can't quite recall exactly how it went). 
Otherwise, have a read of README.DAC960 in the kernel source.

If you don't have the tapes around... a poor man's way of doing it would 
be this.  This is actually how I did it.  The scenario:

Server was a Dual Pentium II 350MHz, 1GB RAM, Symbios SCSI.  Mainboard 
was damaged in the head, resulting in the onboard SCSI playing up 
(throughputs of around ~50KBps).  It was using Linux Software RAID in 
the following configuration (Something along these lines anyway):

	2x IBM 4.5GB SCA SCSI
		-- 20MB	 /boot	RAID-1
		-- 256MB swap	NON-RAID
		-- 4.0GB /	RAID-1
	3x 18.2GB Quantum SCSI HDDs
		-- 256MB swap	NON-RAID
		-- 18GB /home	RAID-1

I had spare, 	1x 4.5GB HP SCA
		1x 18.2GB IBM DGHS SCA

(This could also be done with a single IDE/SCSI HDD of sufficient size)

Compiled the kernel with DAC-960 RAID support.  I plugged in the two 
drives I had and booted up Linux.

Partitioned the temporary drives, formatted them (XFS) and mounted them 
on /mnt.

Copied all of the data onto the drives using tar:
	tar -C / -cv /bin /boot /usr /var /opt /root /home /lib ... -f -
		| tar -C /mnt -xvf -

(Yes, I know cpio could do this for me ... I hadn't discovered it yet at 
this stage)

I then reset up /etc/fstab on the temporary drives and reloaded GRUB on 
them to make them bootable.  I then shut down the server, unplugged the 
original drives and plugged them into the RAID controller.  Once I 
verified the system was booting off the temporary drives, I went into 
Mylex RAID setup and configured the RAID.

Booted off the temporary drives... I then fdisked & formatted the RAID 
arrays before mounting them under /mnt.  Then the above tar command was 
run for a second time to copy the data back.

Once complete, I reconfigred /etc/fstab on the RAID, and re-setup GRUB 
before rebooting.  The server from that point happily booted off the new 
RAID set, so I unplugged the temporary drives and extracted the data off 
for safe keeping. (This was my backup of the server)

	Hopefully this sketchy guide is of some help. ;-)
-- 
+-------------------------------------------------------------+
| Stuart Longland           stuartl at longlandclan.hopto.org |
| Brisbane Mesh Node: 719             http://stuartl.cjb.net/ |
| I haven't lost my mind - it's backed up on a tape somewhere |
| Atomic Linux Project    <--->    http://atomicl.berlios.de/ |
+-------------------------------------------------------------+