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Mode | device before options | Options | Notes |
|---|---|---|---|
| --assemble | Y | bitmap, uuid, super-minor, name, config, scan, run, force, update, no-degraded | |
| --build | Y | ||
| --create | Y | ||
| --grow | N | ||
| --incremental | No options | ||
| --misc | N | ||
| --manage | Y | add, remove, fail, set-faulty, run, stop, readonly, readwrite | --manage may be omitted |
| --monitor | No device |
Troubleshooting
Degraded array report
The system my detect a problem with the array and drop an underlying device. This is normally reported by mail and by Nagios.
It can be confirmed and the excluded underlying device (partition) identified by cat /proc/mdstat
Defects in the physical device may be identified in kern.log and by smartctl -a /dev/sd<letter>
In case smartctl output shows extended tests are not being run (old build computers), update /etc/smarttd.conf from git and edit to suit.
In case no defects are found, there is no choice but to add the excluded underlying device back into the md device as documented under "Replacing an underlying device" above.
If defects are found, ensure the underlying device is not used again by zeroing its md superblock as documented under "Remove an underlying device (md device not in use)" above.
In one case (bafi), during boot an array was assembled from a defective underlying device and the good underlying device excluded.
initrd fails to assemble md devices
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