I recently upgraded an Ubuntu box and noticed that my drives got reordered (possibly by a SATA driver change) and my RAID-1 is degraded. Originally... My (PATA) OS drive had some other partitions and *was* known as /dev/sda. My (SATA) raid-1 /home *was* made from /dev/sdb and /dev/sdc. Now my OS drive is sdc with side effects like mounting some sdc partitions on my old sda mount points. (not a big deal) The real problem is the RAID-1. I think the following 3 queries say: 1) the raid is running with SDA, with the other drive removed. 2) SDA is clean and part of md0 3) SDB is "clean", but part of a raid that doesn't exist. Quote: mastershake:~> sudo mdadm --detail /dev/md0 /dev/md0: Version : 00.90.03 Creation Time : Sun Jan 2 12:53:01 2005 Raid Level : raid1 Array Size : 244195904 (232.88 GiB 250.06 GB) Used Dev Size : 244195904 (232.88 GiB 250.06 GB) Raid Devices : 2 Total Devices : 1 Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Sun Jan 18 23:33:56 2009 State : clean, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 UUID : 61645020:223a69dc:12d77363:0c0f047d Events : 0.5125062 Number Major Minor RaidDevice State 0 8 1 0 active sync /dev/sda1 1 0 0 1 removed Quote: mastershake:~> sudo mdadm --examine /dev/sda1 /dev/sda1: Magic : a92b4efc Version : 00.90.00 UUID : 61645020:223a69dc:12d77363:0c0f047d Creation Time : Sun Jan 2 12:53:01 2005 Raid Level : raid1 Used Dev Size : 244195904 (232.88 GiB 250.06 GB) Array Size : 244195904 (232.88 GiB 250.06 GB) Raid Devices : 2 Total Devices : 1 Preferred Minor : 0 Update Time : Sun Jan 18 23:34:36 2009 State : clean Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 Checksum : e627430d - correct Events : 0.5125064 Number Major Minor RaidDevice State this 0 8 1 0 active sync /dev/sda1 0 0 8 1 0 active sync /dev/sda1 1 1 0 0 1 faulty removed Quote: mastershake:~> sudo mdadm --examine /dev/sdb1 /dev/sdb1: Magic : a92b4efc Version : 00.90.00 UUID : 61645020:223a69dc:12d77363:0c0f047d Creation Time : Sun Jan 2 12:53:01 2005 Raid Level : raid1 Used Dev Size : 244195904 (232.88 GiB 250.06 GB) Array Size : 244195904 (232.88 GiB 250.06 GB) Raid Devices : 2 Total Devices : 2 Preferred Minor : 0 Update Time : Tue Sep 16 07:38:13 2008 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Checksum : e5808830 - correct Events : 0.5048904 Number Major Minor RaidDevice State this 1 8 33 1 active sync /dev/sdc1 0 0 8 17 0 active sync /dev/sdb1 1 1 8 33 1 active sync /dev/sdc1 I've touched files on the degraded md0, so sdb is out-of-date. So what's the safest way to fix this? I've never had to rebuild before. Do I need to fail, remove, then add sdb? Can I mdadm -f /dev/md0 /dev/sdb1 if md0 doesn't thinks sdb is part of it? Or does "removed" in the md0 output mean I don't need to fail and remove, just add? Or do I need to "assemble"? I really don't understand when to use what. Thanks, -troy -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html