Received the following message in mail to root: Message 257: >From root at desk4.localdomain Tue Oct 28 07:25:37 2014 Return-Path: <root at desk4.localdomain> X-Original-To: root Delivered-To: root at desk4.localdomain From: mdadm monitoring <root at desk4.localdomain> To: root at desk4.localdomain Subject: DegradedArray event on /dev/md0:desk4 Date: Tue, 28 Oct 2014 07:25:27 -0400 (EDT) Status: RO This is an automatically generated mail message from mdadm running on desk4 A DegradedArray event had been detected on md device /dev/md0. Faithfully yours, etc. P.S. The /proc/mdstat file currently contains the following: Personalities : [raid1] md0 : active raid1 dm-2[1] 243682172 blocks super 1.1 [2/1] [_U] bitmap: 2/2 pages [8KB], 65536KB chunk md1 : active raid1 dm-3[0] dm-0[1] 1953510268 blocks super 1.1 [2/2] [UU] bitmap: 3/15 pages [12KB], 65536KB chunk unused devices: <none> & q Held 314 messages in /var/spool/mail/root You have mail in /var/spool/mail/root Ran a madam query against both raid partitions: [root at desk4 ~]# mdadm --query --detail /dev/md0 /dev/md0: Version : 1.1 Creation Time : Thu Nov 15 19:24:17 2012 Raid Level : raid1 Array Size : 243682172 (232.39 GiB 249.53 GB) Used Dev Size : 243682172 (232.39 GiB 249.53 GB) Raid Devices : 2 Total Devices : 1 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Tue Dec 2 20:02:55 2014 State : active, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Name : desk4.localdomain:0 UUID : 29f70093:ae78cf9f:0ab7c1cd:e380f50b Events : 266241 Number Major Minor RaidDevice State 0 0 0 0 removed 1 253 3 1 active sync /dev/dm-3 [root at desk4 ~]# [root at desk4 ~]# mdadm --query --detail /dev/md1 /dev/md1: Version : 1.1 Creation Time : Thu Nov 15 19:24:19 2012 Raid Level : raid1 Array Size : 1953510268 (1863.01 GiB 2000.39 GB) Used Dev Size : 1953510268 (1863.01 GiB 2000.39 GB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Tue Dec 2 20:06:21 2014 State : active Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Name : desk4.localdomain:1 UUID : 1bef270d:36301a24:7b93c7a9:a2a95879 Events : 108306 Number Major Minor RaidDevice State 0 253 0 0 active sync /dev/dm-0 1 253 1 1 active sync /dev/dm-1 [root at desk4 ~]# Appears to me that device 0 (/dev/dm-2) on md0 has been removed because of problems. This is my first encounter with a raid failure. I suspect I should replace disk 0 and let the raid rebuild itself. Seeking guidance and a good source for the procedures. Dave M