{{tag>[linux mdadm raid raid1 failed disk centos7]}}
=====mdadm - replace failed RAID1 disk=====
====Check and remove disk====
* Check status:# cat /proc/mdstat
Personalities : [raid1]
md125 : active raid1 sdb3[1]
450747264 blocks super 1.2 [2/1] [_U]
md126 : active raid1 sdb2[1]
36949888 blocks super 1.2 [2/1] [_U]
bitmap: 1/1 pages [4KB], 65536KB chunk
md127 : active raid1 sdb1[1]
524224 blocks super 1.0 [2/1] [_U]
unused devices:
* /dev/sda seems missing, check dmesg:# dmesg |grep sda
[2212380.750253] end_request: I/O error, dev sda, sector 2048
[2212380.750263] md/raid1:md127: Disk failure on sda1, disabling device.
* Or with smartctl:# smartctl /dev/sda
smartctl 6.2 2013-07-26 r3841 [x86_64-linux-3.10.0-229.1.2.el7.x86_64] (local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke, www.smartmontools.org
Smartctl open device: /dev/sda failed: No such device
* Remove the drive from the array if it isn't already removed. Seems md already diabled my drive:messages-20150504.gz:May 3 00:41:06 kvm2 kernel: md/raid1:md126: Disk failure on sda2, disabling device.
messages-20150504.gz:May 3 00:41:06 kvm2 kernel: md/raid1:md125: Disk failure on sda3, disabling device.
messages-20150504.gz:May 3 01:02:01 kvm2 kernel: md/raid1:md127: Disk failure on sda1, disabling device.
* Check the serial number for the **good** drive:]# smartctl -a /dev/sdb |grep -i serial
Serial Number: 9WJ0MGBM
====Replace drive====
* Replace the failed drive, double check the serial number on the drive.
* Copy boot sector / partition table to new drive:sfdisk -d /dev/sdb | sfdisk /dev/sda
====Rebuild RAID1 array====
* Put new drive in array:mdadm /dev/md125 -a /dev/sda3
mdadm /dev/md126 -a /dev/sda2
mdadm /dev/md127 -a /dev/sda1
grub2-install --recheck /dev/sda
* Watch /proc/mdstat:# cat /proc/mdstat
Personalities : [raid1]
md125 : active raid1 sda3[2] sdb3[1]
450747264 blocks super 1.2 [2/1] [_U]
[>....................] recovery = 0.0% (121856/450747264) finish=6938.0min speed=1082K/sec
md126 : active raid1 sda2[2] sdb2[1]
36949888 blocks super 1.2 [2/1] [_U]
resync=DELAYED
bitmap: 1/1 pages [4KB], 65536KB chunk
md127 : active raid1 sda1[2] sdb1[1]
524224 blocks super 1.0 [2/1] [_U]
resync=DELAYED
unused devices:
====Speed up rebuild====
* Show current min/max limit:sysctl dev.raid.speed_limit_min
sysctl dev.raid.speed_limit_max
* Increase speed:sysctl -w dev.raid.speed_limit_min=100000