3.4. Additional Configuration Issues

During the hardware installation of Linux FailSafe nodes, two additional issues must be considered:

• The Linux FailSafe software requires the nodes to be automatically booted when they are reset or when the node is powered on. Linux on x86 will be dependent upon BIOS configuration to ensure this. Some PC BIOSes will hang indefinitely upon error. Clearly this is not useful for high availability situations. On other platforms, such as PowerPC, Alpha, etc, the necessary steps will vary.

  A related, but not identical issue is that of reboots on kernel panics. To ensure the system will reboot even in the case of a kernel failure, set the panic value in a system boot file, such as init.d/boot.local:

  echo "number" > /proc/sys/kernel/panic

  number is the number of seconds after a panic before the system will reset.

  If you would prefer administrator intervention to be required during a hardware or kernel failure, you may leave this disabled

• The SCSI controllers' host IDs of the nodes in a Linux FailSafe cluster using physically shared storage must be different. If a cluster has no shared storage or is using shared Fibre Channel storage, the value of SCSI host ID is not important.

You can check the ID of most Linux controllers in the logged kernel messages from boot time:

# grep ID= /var/log/messages 
<6>(scsi0) Wide Channel, SCSI ID=7, 16/255 SCBs

Changing the SCSI host ID is specific to the SCSI controller in use. Refer to the controller documentation.

A controller uses its SCSI ID on all buses attached to it. Therefore, you must make sure that no device attached to a node has the same number as its SCSI unit number.