mark the drive as failed first mdadm /dev/mdX -f /dev/sdYX Power down and physically replace faulty drive. Make sure the partitions are properly aligned, as in http://www.ibm.com/developerworks/linux/library/l-4kb-sector-disks/#tools Boot and partition new drive, and if you want to partition the new drive similar as others, you can do it with.. sfdisk -d /dev/sdX | sfdisk /dev/sdY mdadm … Continue reading Replacing failed disk in software RAID