---
title: Scrappy notes about RAID & mdadm
date: 2020-08-27
---
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## Recover from a disk failure

Below is "what worked last time", but there is more comprehensive documentation [elsewhere](https://raid.wiki.kernel.org/index.php/RAID_Recovery).

Disconnect the existing RAID array:

```
$ mdadm --stop /dev/md127
```

Create a new array out of the working disks:

```
$ mdadm \
    --verbose \
    --assemble \
    --force \
    /dev/md0 \
    /dev/sdc1 /dev/sdd1
```

Try mounting it, check everything's OK:

```
$ mount /dev/md0 /mnt/md0
```

Add the new disk:

```
$ mdadm --manage /dev/md0 --add /dev/sdb1
```

Watch it rebuild, and hope:

```
$ cat /proc/mdstat
```

## Misc

### Identify a physical disk

```
$ hdparm -I /dev/sda | grep Serial 
```
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