Hi, I've been setting up a RAID1 (Ubuntu software RAID) and a fileserver ubuntu server 12.04.5/samba I made a test where I yanked drive 0 out to see if the other disk would work/take over (to test the RAID1). Then I shutdown the system and installed the disk again. The RAID still works but when testing using these commands, I get these funne results. md1 state shows "clean, degraded" !?!? And, MD1 also shows "removed" where "active sync /dev/sdb2" should have been. The disk I "removed" (physically, not a command) was disk0 where theres a part of MD0 and MD1 on. I made 2 x 2Gb swapfile on each disk and 2 x 495Gb Ext4 (bootable) for the data. (Building a fileserver) I re-added (physically, not a command) the disk and have read that it should re-sync itself: ".....Sometimes a disk can change to a faulty state even though there is nothing physically wrong with the drive. It is usually worthwhile to remove the drive from the array then re-add it. This will cause the drive to re-sync with the array. If the drive will not sync with the array, it is a good indication of hardware failure..." https://help.ubuntu.com/12.04/serverguide/advanced-installation.html#raid-maintenance Code: # mdadm -D /dev/md0 /dev/md0: Version : 1.2 Creation Time : Sun Aug 24 06:03:45 2014 Raid Level : raid1 Array Size : 1950656 (1905.26 MiB 1997.47 MB) Used Dev Size : 1950656 (1905.26 MiB 1997.47 MB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Update Time : Sun Aug 24 06:44:28 2014 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Name : whitley:0 UUID : 712d496a:18bddce6:1248aafd:cab10a66 Events : 17 Number Major Minor RaidDevice State 0 8 1 0 active sync /dev/sda1 1 8 17 1 active sync /dev/sdb1 # mdadm -D /dev/md1 /dev/md1: Version : 1.2 Creation Time : Sun Aug 24 06:04:08 2014 Raid Level : raid1 Array Size : 483267392 (460.88 GiB 494.87 GB) Used Dev Size : 483267392 (460.88 GiB 494.87 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Update Time : Sun Aug 24 11:11:11 2014 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : whitley:1 UUID : 7e1f4b1b:d9351351:7ee5ff14:5bf84c84 Events : 158 Number Major Minor RaidDevice State 0 8 2 0 active sync /dev/sda2 1 0 0 1 removed Code: # watch -n1 cat /proc/mdstat Every 1.0s: cat /proc/mdstat Sun Aug 24 11:32:17 2014 Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [ra id10] md0 : active raid1 sda1 sdb1 1950656 blocks super 1.2 [2/2] [UU] md1 : active raid1 sda2 483267392 blocks super 1.2 [2/1] [U_] unused devices: <none> Hope you can help me. I you need info, plase don't hesitate to say so, and I will provide it for you NB! The sync was completed .