[root@sd /]# mdadm --fail /dev/md0 /dev/sdb1 mdadm: set /dev/sdb1 faulty in /dev/md0 [root@sd /]# mdadm -f /dev/md0 /dev/sdb1 mdadm: set /dev/sdb1 faulty in /dev/md0 [root@sd /]# mdadm --remove /dev/md0 /dev/sdb1 mdadm: hot removed /dev/sdb1 [root@sd /]# mdadm -r /dev/md0 /dev/sdb1 mdadm: hot remove failed for /dev/sdb1: No such device or address [root@sd /]# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sda1[1] 7350592 blocks [2/1] [_U] unused devices: +++ sdb@FAT32 format +++ [root@sd /]# fdisk /dev/sdc Command (m for help): o Building a new DOS disklabel with disk identifier 0xdad3378b. Changes will remain in memory only, until you decide to write them. After that, of course, the previous content won't be recoverable. Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite) Command (m for help): p Disk /dev/sdc: 8010 MB, 8010072064 bytes 247 heads, 62 sectors/track, 1021 cylinders Units = cylinders of 15314 * 512 = 7840768 bytes Disk identifier: 0xdad3378b Device Boot Start End Blocks Id System Disk /dev/sdc: 8010 MB, 8010072064 bytes 247 heads, 62 sectors/track, 1021 cylinders Units = cylinders of 15314 * 512 = 7840768 bytes Disk identifier: 0xdad3378b Device Boot Start End Blocks Id System /dev/sdc1 * 1 960 7350689 fd Linux raid autodetect /dev/sdc2 961 1021 467077 82 Linux swap / Solaris Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks. [root@sd /]# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sda1[1] 7350592 blocks [2/1] [_U] unused devices: [root@sd /]# mdadm /dev/md0 --add /dev/sdc1 mdadm: re-added /dev/sdc1 [root@sd /]# cat /proc/mdstat Personalities : [raid1] md0 : active raid1 sdc1[2] sda1[1] 7350592 blocks [2/1] [_U] [>....................] recovery = 0.0% (6976/7350592) finish=52.4min speed=2325K/sec unused devices: [root@sd /]#