CH3SNAS: Degraded Raid Status

January 7, 2008

In some very rare conditions (I still did not found when and why) it’s possible that a RAID1 array made onto the CH3SNAS gets into a degraded status and even a reboot is not solving the issue.

How to get the RAID array fixed again?

First of all: make sure you have telnet running. Telnet can be installed by using one of the many fun_plugs around. So no explanation from me about that.

Login to the shell

first check the actual raid status:

 # cat /proc/mdstat

Normally you should get something like this: 

Personalities : [linear] [raid0] [raid1]
md0 : active raid1 sda2[0] sdb2[1]
xxxxx blocks [2/2] [UU]

But when degraded the raid status shows: [_U] or [U_]

Do some debugging with the command:

# mdadm -D /dev/md0

This will show the actual HDD’s in the array. For the CH3SNAS it can be:

/dev/sda2 or /dev/sdb2 if one of the disks is not in the array anymore you have to add it manually by using the following command:

mdadm /dev/md0 -a [degraded hdd]

this is: /dev/sdb2 or /dev/sda2

System will report: 

mdadm: hot added /dev/sdb2; and the array will be synced again (seen through webinterface or using the `# cat /proc/mdstat command`)

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Posted in Work
Tags: ch3snas, conceptronic, degraded, landisk, nas, raid