Re: raid device gone underneath array

[Brad Campbell <lists2009@fnarfbargle.com>]

On 19/10/12 12:03, Chris Dunlop wrote:
> On 2012-10-19, Adam Goryachev <mailinglists@websitemanagers.com.au> wrote:
>> On 19/10/12 11:01, Marcus Sorensen wrote:
>>> I've been using software raid to mirror two devices, and recently one
>>> of the drives went AWOL.
>>>
>>> md1 : active raid1 sdm[0] sdc[1](F)
>>>        12884900728 blocks super 1.2 [2/1] [U_]
>>>        bitmap: 1/96 pages [4KB], 65536KB chunk
>>>
>>> However, md1 froze, and in looking at the logs I saw this:
>>>
>>> Oct 18 17:47:48 sys kernel: md: cannot remove active disk sdc from md1 ...
>>> Oct 18 17:47:48 sys kernel: md: cannot remove active disk sdc from md1 ...
>>>
>>> [root(marcus)@sanmirror3-01 ~]# mdadm --manage /dev/md1 --remove /dev/sdc
>>> mdadm: cannot find /dev/sdc: No such file or directory
>>>
>>> /dev/sdc was already gone! The /sys/block was already removed, no
>>> reference to it in /proc/scsi/scsi. So md1 was destined to sit there
>>> forever. So I rebooted and started up the degraded array.
>>>
>>> Using kernel 3.6.2 from kernel.org
>>
>> I've also had this problem, I think the kernel notices the device is
>> gone, and removes it before MD notices the problem and removes it from
>> the array. I managed to resolve this without a reboot by manually
>> creating the device in /dev/sdc1 or whatever, and then doing mdadm
>> --manage /dev/md0 --remove /dev/sdc1
>
> Or you could simply do:
>
> mdadm --manage /dev/md1 -r failed

or for two less keystrokes

mdadm --remove /dev/md1 failed