There are some cases, where a failed drive in our RAID array can cause serious issues. For example, due to the failed drive, our Linux system can shutdown and it won't be able to boot again. The GRUB bootloader might also fail and will need to be reinstalled. We have few options, one of which is to reassemble our RAID array from any other Linux LiveCD distribution. Of course, first we need to physically replace the failed drive and then boot to our LiveCD. Once we have booted, we need to install the mdadm tool.