Managing RAID on Linux - Derek Vadala [95]
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Configuring an existing disk for JBOD mode
Adaptec RAID controllers support JBOD mode by default. So if you replace an existing SCSI controller with an Adaptec RAID controller, your existing single-disk system will boot normally. You still need to reconfigure and recompile your kernel so it supports either the dpt_i2o or the aacraid driver. Don't forget to rerun /sbin/lilo.
I recommend adding support for your Adaptec controller while your disks are still connected to your original SCSI controller. Restart the system and make sure your kernel still works with your original configuration. Next, shut down the system and replace the SCSI controller with your Adaptec RAID controller, connecting your system disks to the RAID controller. Be certain that your system disk is still the first disk after you reconnect to the RAID controller. When you power on the system, Linux should boot normally, provided that the kernel was compiled properly. If you encounter problems, you can revert to your original hardware configuration and troubleshoot.
Converting an existing standalone disk to a mirror
If you want to upgrade an existing system with a single disk to a RAID-1, using an Adaptec RAID controller, you should first compile a new kernel with support for the dpt_i2o or aacraid driver. Consult the driver sections earlier in this chapter for more information. It's okay to leave the driver for your existing SCSI controller compiled into the kernel. In fact, that will make it easier to revert back to your original configuration if you encounter any problems. After the driver is enabled, and the new kernel is installed, follow these steps:
Reconfigure your kernel so that it supports either the dpt_i2o driver or the aacraid driver, depending on which controller you have.
Reboot the system and use CTRL-A to enter the Adaptec RAID Setup Utility.
After the utility initializes and scans the connected disks, press ALT-R to activate the RAID configuration menu.
Select Create from the RAID configuration menu. A window that lists the available RAID levels and the default stripe size will appear.
Use the TAB or arrow keys to move between each option. Pressing the SPACEBAR selects the RAID level that is currently highlighted. Choose RAID-1.
Navigate to the Okay button and press ENTER to confirm the RAID configuration.
The next screen lists available disks. Use the ENTER key to select your existing system disk, as well as a second disk to include in the mirror. Move up and down the list using the arrow keys. When a disk is selected, a checkmark appears to its left.
When you are finished selecting disks, navigate to the Done button, using the TAB key, and press ENTER to create the new array.
A dialog will appear, asking in which direction the initial resynchronization should move. Two choices are presented. Synchronize from the first disk to the second, or synchronize from the second disk to the first. This choice is extremely important. If you make the wrong decision, it will result in a total loss of data. Make certain that data is copied from your existing system disk to the new disk. Generally, this means copying data from disk 0,0,0,0 (the disk with the existing system data) to disk 0,0,1,0 (the second blank hard disk).
An additional dialog appears, indicating that there is valid data on at least one of the disks. That's because the first disk, at least, contains a valid partition table and a boot sector. The second disk might also contain some residual but expendable data. After confirming these additional dialogs, you are returned to the Adaptec RAID Setup Utility's main menu. The new array appears in the left column just below the controller's entry. You can use the ENTER key to expand and collapse the array's entry, in order to reveal its member disks.
Finally, press