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mdadm: added raid 5

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tiyn 2023-03-22 15:42:59 +01:00
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@ -20,6 +20,7 @@ be a whole drive and the mdadm drive is called `/dev/md0`.
### Raid 1
Raid 1 creates a mirror with even amount of drives.
For `n=2` [raid 5](#raid-5) and raid 1 are basically the same.
#### Create raid 1 device
@ -31,11 +32,14 @@ If it is an uneven amount of disks in the raid, a disk will act as a spare disk.
#### Convert raid 1 to raid 5
Assuming the raid device is called `/dev/md0`.
Assuming the raid 1 device is called `/dev/md0`.
All other drives are part of the `md0` raid device.
Note that mostly raid 1 devices consisting of 2 drives should be converted to
[raid 5](#raid-5).
- Remove all drives but 2 by running `mdadm /dev/md0 --fail /dev/sda1` and
`mdadm /dev/md0 --remove /dev/sda1` where `sda1` is the drive to remove
- Remove all drives but 2 (if there are more drives than that) by running
`mdadm /dev/md0 --fail /dev/sda1` and `mdadm /dev/md0 --remove /dev/sda1`
where `sda1` is the drive to remove
- Make sure your raid 1 array has only 2 active drives by running
`mdadm --grow /dev/md0 -n 2`
- Now convert your raid 1 to a raid 5 device with `mdadm --grow /dev/md0 -l5`
@ -45,3 +49,10 @@ All other drives are part of the `md0` raid device.
`mdadm --grow /dev/md0 -n4`
- `mdadm` now reshapes the raid. You can monitor it by running
`watch cat /proc/mdstat`
### Raid 5
Raid 5 creates a raid device with distributed parity.
For `n>1` drives with the same size it creates a raid device with the size `n-1`
drives.
For `n=2` raid 5 and [raid 1](#raid-1) are basically the same.