Changing Hard Drive controllers with s/w RAI
 

I have a server with an onboard SymBIOS SCSI controller. It only supports up 40mb xfers. However, I have two U160 IBM SCSI drives mirrored together through the Linux s/w RAID tools (ie md0, md1, etc). on this controller. I have recently purchased an Adaptec U160 capable SCSI controller and want to install it and simply move the SCSI ribbon from the onboard controller to the newer, faster controller.

Does anyone see this as a major issue? Aside from ensuring my kernel has support for the new controller compiled in, will anything break? I'm used to the Sun/BSD world that assigns device IDs in the c0t0d0s0 fashion. Hence if c0 is the onboard controller and c1 becomes the new controller, and I move stuff over, it won't boot up w/o being reconfigured 'cause it's looking for a disk on c0. This is similar to how NT/2000 works. Is Linux the same? Are the c0t0d0s0 settings all just hidden from me? Or does controller order not matter if I only have one boot disk? I have lilo installed and the root dev is /dev/md4. Is the controller stuff hidden somewhere? Maybe /etc/raidtab?

I've done this a bunch with IDE controllers, onboard and cards... If you're able to disable that onboard scsi card in BIOS, then the kernel should never detect it and then it will see the new scsi card the same as the old, probably /dev/sda1, sda2, then treat them as raid devices and detect them normally. It's no big deal really, watch dmesg scroll past on boot and see if it registers the new card with the right scsi ID, and if it doesn't, take note of where it is now, switch the drive back, boot, fix fstab and raidtab for where they will be, shutdown, switch, and you should be good to go.

Sometimes the kernel outguesses you. For instance I recently switched everything on my machine onto my ATA100 controller thinking that disabling the onboard IDEs in BIOS would keep the kernel from seeing them at all, it did anyway and I had to hack up my fstab as the boot drive went from /dev/hda to /dev/hde.

However, I've got a friends PPro with onboard SCSI, and I just disabled the SCSI from bios, put in a new card, switched the drives, and it kept its position as /dev/sda.

Alot of BIOS voodoo and luck is involved.

Cheers,

Finegan