I have 2 sata 300 gb hard drives mirrored - all partitions are mirrored. this weekend the home (md6) partition lost one of its members (sda8) but sda did not fail only one partition. So I assume i need to hot add back in sda8 to md6 and from the mdadm man page i got # /sbin/mdadm /dev/md6 -a /dev/sda8 mdadm: Cannot open /dev/sda8: Device or resource busy am I doing something wrong??? This is the first time i have used mdadm to manage raid. do i have to unmount md6?? -chris extra info below # /sbin/mdadm -D /dev/md6 /dev/md6: Version : 00.90.01 Creation Time : Sat Aug 27 21:16:47 2005 Raid Level : raid1 Array Size : 228420096 (217.84 GiB 233.90 GB) Device Size : 228420096 (217.84 GiB 233.90 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 6 Persistence : Superblock is persistent Update Time : Mon Jan 23 16:10:35 2006 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 UUID : dd8c6a34:5c54af22:1c287ca5:c8cf4219 Events : 0.3277181 Number Major Minor RaidDevice State 0 0 0 - removed 1 8 24 1 active sync /dev/sdb8 2 8 8 - faulty /dev/sda8 -------------------------------------- messages log Jan 22 13:17:21 agwebinc kernel: ata1: command 0x25 timeout, stat 0x51 host_stat 0x21 Jan 22 13:17:21 agwebinc kernel: ata1: status=0x51 { DriveReady SeekComplete Error } Jan 22 13:17:21 agwebinc kernel: ata1: error=0x04 { DriveStatusError } Jan 22 13:17:21 agwebinc kernel: SCSI error : <0 0 0 0> return code = 0x8000002 Jan 22 13:17:21 agwebinc kernel: sda: Current: sense key: Aborted Command Jan 22 13:17:21 agwebinc kernel: Additional sense: No additional sense information Jan 22 13:17:21 agwebinc kernel: end_request: I/O error, dev sda, sector 159199891 Jan 22 13:17:21 agwebinc kernel: raid1: Disk failure on sda8, disabling device. Jan 22 13:17:21 agwebinc kernel: Operation continuing on 1 devices Jan 22 13:17:21 agwebinc kernel: raid1: sda8: rescheduling sector 29972968 Jan 22 13:17:21 agwebinc kernel: raid1: sdb8: redirecting sector 29972968 to another mirror Jan 22 13:17:21 agwebinc kernel: RAID1 conf printout: Jan 22 13:17:21 agwebinc kernel: --- wd:1 rd:2 Jan 22 13:17:21 agwebinc kernel: disk 0, wo:1, o:0, dev:sda8 Jan 22 13:17:21 agwebinc kernel: disk 1, wo:0, o:1, dev:sdb8 Jan 22 13:17:21 agwebinc kernel: RAID1 conf printout: Jan 22 13:17:21 agwebinc kernel: --- wd:1 rd:2 Jan 22 13:17:21 agwebinc kernel: disk 1, wo:0, o:1, dev:sdb8 --------------------------------------- mdstat [root@agwebinc usbdisk]# cat /proc/mdstat Personalities : [raid1] md5 : active raid1 sdb1[1] sda1[0] 104320 blocks [2/2] [UU] md1 : active raid1 sdb3[1] sda3[0] 15358016 blocks [2/2] [UU] md2 : active raid1 sdb5[1] sda5[0] 15358016 blocks [2/2] [UU] md3 : active raid1 sdb6[1] sda6[0] 8193024 blocks [2/2] [UU] md4 : active raid1 sdb7[1] sda7[0] 5116544 blocks [2/2] [UU] md6 : active raid1 sdb8[1] sda8[2](F) 228420096 blocks [2/1] [_U] md0 : active raid1 sdb2[1] sda2[0] 20482752 blocks [2/2] [UU] unused devices: <none> ------------------------------------------------------- # /sbin/mdadm --examine /dev/sda8 /dev/sda8: Magic : a92b4efc Version : 00.90.01 UUID : dd8c6a34:5c54af22:1c287ca5:c8cf4219 Creation Time : Sat Aug 27 21:16:47 2005 Raid Level : raid1 Raid Devices : 2 Total Devices : 2 Preferred Minor : 6 Update Time : Sun Jan 22 13:16:52 2006 State : active Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Checksum : 5cb7ffc9 - correct Events : 0.3226885 Number Major Minor RaidDevice State this 0 8 8 0 active sync /dev/sda8 0 0 8 8 0 active sync /dev/sda8 1 1 8 24 1 active sync /dev/sdb8 ------------------------------------------------------- # /sbin/mdadm --examine /dev/sdb8 /dev/sdb8: Magic : a92b4efc Version : 00.90.01 UUID : dd8c6a34:5c54af22:1c287ca5:c8cf4219 Creation Time : Sat Aug 27 21:16:47 2005 Raid Level : raid1 Raid Devices : 2 Total Devices : 2 Preferred Minor : 6 Update Time : Mon Jan 23 16:27:14 2006 State : clean Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 Checksum : 5cec4a0d - correct Events : 0.3277961 Number Major Minor RaidDevice State this 1 8 24 1 active sync /dev/sdb8 0 0 0 0 0 removed 1 1 8 24 1 active sync /dev/sdb8