mdadm management instructions v1

Author: root

tutorials/mdadm/mdadm_initial_configuration.md

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+# mdadm
+### _Configuring Software raid ([link](https://www.thegeekdiary.com/redhat-centos-managing-software-raid-with-mdadm/))_
+
+We need to make sure all disks have the same partition layout:
+```
+sfdisk -d /dev/sdb | sfdisk /dev/sdc
+```
+
+Now create the RAID device using mdadm
+```
+mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
+```
+
+Format the drive and mount it (dir will need to exist)
+```
+mke2fs -j /dev/md0 && mount /dev/md0 /data01
+```
+
+Add fstab entry so persists across reboots
+```
+/dev/md0       /data01         ext4    defaults        0    0
+```
+
+### Verifying the config
+
+/proc/mdstat is a file maintained by the kernel which contains the real time information about the RAID arrays and devices.
+```
+cat /proc/mdstat
+```
+
+If you want some more detailed info use mdadm
+```
+mdadm --detail /dev/md0
+```

tutorials/mdadm/mdadm_management.md

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+# Managing mdadm
+
+### Add and remove devices
+
+To add a device
+```
+mdadm --add /dev/md0 /dev/sdd
+```
+
+To remove a device (-f fail device, -r remove device)
+```
+# mdadm --manage /dev/md0 -f /dev/sdd
+# mdadm --manage /dev/md0 -r /dev/sdd
+```
+
+### Replacing failed mirror disk ([link](https://www.thegeekdiary.com/replacing-a-failed-mirror-disk-in-a-software-raid-array-mdadm/))
+
+Before removing raid disks we need to run the following command to write all disk caches to the disk
+```
+sync    
+```
+
+Mark as failed
+```
+mdadm --manage /dev/md0 --fail /dev/sdb1
+```
+
+Check /proc/mdstat to make sure the disk has been marked as failed (F)
+```
+# cat /proc/mdstat
+
+Personalities : [linear] [multipath] [raid0] [raid1] [raid5] [raid4] [raid6] [raid10]
+
+md0 : active raid1 sda1[0] sdb1[2]**(F)**
+
+      976773168 blocks [2/1] [U_]
+
+The \*\*(F)\*\* shows the disk has failed
+
+We can now physically remove the disk and replace
+```
+_Remove and replace disk_
+```
+
+We now need to copy the partition table to the newly replaced disk
+```
+sfdisk -d /dev/sda | sfdisk /dev/sdb
+```
+
+Create a mirror of the disk
+```
+mdadm /dev/md0 --add /dev/sdb1
+```
+
+Test the setup
+```
+mdadm --detail /dev/md0
+```
+
+Finally check the progress of the recovery
+```
+cat /proc/mdstat
+```