you should probably do cat /proc/mdstat
It is likely that the livecd may have already tried to assemble it,
and that the busy is because it is already in use.
If it is already assembled and you want to redo it first you will need
to stop the assembled array to be able to redo it.
On Thu, Mar 26, 2015 at 6:52 PM, Dave Stevens <geek@xxxxxxxxxxxx> wrote:
> Hello list, Phil,
>
> I read your advice in the text below and it seems very reasonable. I want to
> do a test to see if the data is readable and this is what I did with the
> live distro:
>
> mdadm -A /dev/md13 /dev/sdb2 /dev/sdc2
>
> and then mdadm said:
>
> mdadm: can not open device /dev/sdb2: device or resource busy
> mdadm: /dev/sdb2 has no superblock - assembly aborted
>
> I don't know if these errors are related - i.e., if there is no superblock
> is that the busy resource in the first message? And if the superblock is
> absent can I put it back or somehow recreate it?
>
> Dave
>
>
>
>
>
>
> From: Phil Turmel <philip@xxxxxxxxxx>
> To: Dave Stevens <geek@xxxxxxxxxxxx>, linux-raid@xxxxxxxxxxxxxxx
> Subject: Re: two raid issues
> Date: Sun, 08 Mar 2015 09:52:04 -0400
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
> Thunderbird/31.5.0
>
> Good morning Dave,
>
> On 03/07/2015 05:42 PM, Dave Stevens wrote:
>>
>> Hello the raid list,
>>
>> I have inherited a server set up by people who are no longer around. It
>> worked fine until recently and then after a routine update refused to
>> boot. I've got the machine in my office and have been examining the
>> problem, or rather problems, I think there are two.
>
>
> Three, at least.
>
>> First, the bootable partition on /dev/sda1 won't successfully boot to a
>> xen kernel, kernel version is 2.6.18.something-xen. The intent is to
>> boot to a raid-10 array of four 750GB drives, each partitioned into a
>> small and a large partition as detailed below.
>>
>> Boot proceeds normally according to on-screen messages until this:
>>
>> md: md0: raid array is not clean -- starting background reconstruction
>> raid10: not enough operational mirrors for md0
>> md: pers -> () failed
>
>
> Yup. Degraded to the point of not running.
>
>> Immediately after these messages is another stating that an attempt has
>> been made to kill init, kernel panic and reboot.
>
>
> No way to pivot to your root filesystem, so your initramfs gives up.
> Depending on the distro, it may be possible to pass a kernel command
> line option to drop into a repair shell at that point.
>
>> I've tried to give these messages verbatim but have no way (I think) to
>> reproduce them other than manually.
>
>
> Repair shell, if available.
>
>> So at first I looked around, read through the wiki and found advice to
>> NOT write anything to the array, which seems reasonable. I looked at a
>> live microknoppix distro called runtime live that gave me a command
>> shell to run the examine command with the output below:
>
>
> LiveCD boot is good, and the following report is very detailed, thanks:
>
>> /dev/sda2:
>> Magic : a92b4efc
>> Version : 0.90.00
>> UUID : a9bde90a:77abaef6:6c6fe013:77d6cdaf
>> Creation Time : Sun Nov 29 15:33:50 2009
>> Raid Level : raid10
>> Used Dev Size : 732467456 (698.54 GiB 750.05 GB)
>> Array Size : 1464934912 (1397.07 GiB 1500.09 GB)
>> Raid Devices : 4
>> Total Devices : 3
>> Preferred Minor : 0
>>
>> Update Time : Wed Feb 18 19:28:22 2015
>> State : active
>> Active Devices : 2
>> Working Devices : 2
>> Failed Devices : 2
>> Spare Devices : 0
>> Checksum : 7c76593b - correct
>> Events : 32945477
>
>
> This is important: ^^^^^^^^
>
>> Layout : near=2
>> Chunk Size : 256K
>>
>> Number Major Minor RaidDevice State
>> this 0 8 2 0 active sync /dev/sda2
>>
>> 0 0 8 2 0 active sync /dev/sda2
>> 1 1 0 0 1 active sync
>> 2 2 8 34 2 active sync /dev/sdc2
>> 3 3 0 0 3 faulty removed
>> /dev/sdb2:
>> Magic : a92b4efc
>> Version : 0.90.00
>> UUID : a9bde90a:77abaef6:6c6fe013:77d6cdaf
>> Creation Time : Sun Nov 29 15:33:50 2009
>> Raid Level : raid10
>> Used Dev Size : 732467456 (698.54 GiB 750.05 GB)
>> Array Size : 1464934912 (1397.07 GiB 1500.09 GB)
>> Raid Devices : 4
>> Total Devices : 3
>> Preferred Minor : 0
>>
>> Update Time : Sat Nov 22 13:18:12 2014
>> State : clean
>> Active Devices : 3
>> Working Devices : 3
>> Failed Devices : 1
>> Spare Devices : 0
>> Checksum : 7d850ca4 - correct
>> Events : 32945477
>
>
> With this: ^^^^^^^^
>
>> Layout : near=2
>> Chunk Size : 256K
>>
>> Number Major Minor RaidDevice State
>> this 1 8 18 1 active sync /dev/sdb2
>>
>> 0 0 8 2 0 active sync /dev/sda2
>> 1 1 8 18 1 active sync /dev/sdb2
>> 2 2 8 34 2 active sync /dev/sdc2
>> 3 3 0 0 3 faulty removed
>> /dev/sdc2:
>> Magic : a92b4efc
>> Version : 0.90.00
>> UUID : a9bde90a:77abaef6:6c6fe013:77d6cdaf
>> Creation Time : Sun Nov 29 15:33:50 2009
>> Raid Level : raid10
>> Used Dev Size : 732467456 (698.54 GiB 750.05 GB)
>> Array Size : 1464934912 (1397.07 GiB 1500.09 GB)
>> Raid Devices : 4
>> Total Devices : 3
>> Preferred Minor : 0
>>
>> Update Time : Wed Feb 18 19:30:13 2015
>> State : active
>> Active Devices : 1
>> Working Devices : 1
>> Failed Devices : 2
>> Spare Devices : 0
>> Checksum : 7c7659de - correct
>> Events : 32945479
>
>
> And this: ^^^^^^^^
>
>> Layout : near=2
>> Chunk Size : 256K
>>
>> Number Major Minor RaidDevice State
>> this 2 8 34 2 active sync /dev/sdc2
>>
>> 0 0 0 0 0 removed
>> 1 1 0 0 1 faulty removed
>> 2 2 8 34 2 active sync /dev/sdc2
>> 3 3 0 0 3 faulty removed
>> /dev/sdd2:
>> Magic : a92b4efc
>> Version : 0.90.00
>> UUID : a9bde90a:77abaef6:6c6fe013:77d6cdaf
>> Creation Time : Sun Nov 29 15:33:50 2009
>> Raid Level : raid10
>> Used Dev Size : 732467456 (698.54 GiB 750.05 GB)
>> Array Size : 1464934912 (1397.07 GiB 1500.09 GB)
>> Raid Devices : 4
>> Total Devices : 5
>> Preferred Minor : 0
>>
>> Update Time : Wed Sep 4 07:51:50 2013
>> State : active
>> Active Devices : 4
>> Working Devices : 5
>> Failed Devices : 0
>> Spare Devices : 1
>> Checksum : 77c1a3a7 - correct
>> Events : 53
>
>
> Whoa! ^^^^
>
>> Layout : near=2
>> Chunk Size : 256K
>>
>> Number Major Minor RaidDevice State
>> this 3 8 50 3 active sync /dev/sdd2
>>
>> 0 0 8 2 0 active sync /dev/sda2
>> 1 1 8 18 1 active sync /dev/sdb2
>> 2 2 8 34 2 active sync /dev/sdc2
>> 3 3 8 50 3 active sync /dev/sdd2
>> 4 4 8 66 4 spare /dev/sde2
>> /dev/sde2:
>> Magic : a92b4efc
>> Version : 0.90.00
>> UUID : a9bde90a:77abaef6:6c6fe013:77d6cdaf
>> Creation Time : Sun Nov 29 15:33:50 2009
>> Raid Level : raid10
>> Used Dev Size : 732467456 (698.54 GiB 750.05 GB)
>> Array Size : 1464934912 (1397.07 GiB 1500.09 GB)
>> Raid Devices : 4
>> Total Devices : 5
>> Preferred Minor : 0
>>
>> Update Time : Sun Sep 8 13:25:42 2013
>> State : clean
>> Active Devices : 4
>> Working Devices : 4
>> Failed Devices : 0
>> Spare Devices : 0
>> Checksum : 77c775be - correct
>> Events : 7934
>
>
> And Whoa again! ^^^^^^
>
>> Layout : near=2
>> Chunk Size : 256K
>>
>> Number Major Minor RaidDevice State
>> this 3 8 66 3 active sync /dev/sde2
>>
>> 0 0 8 2 0 active sync /dev/sda2
>> 1 1 8 18 1 active sync /dev/sdb2
>> 2 2 8 34 2 active sync /dev/sdc2
>> 3 3 8 66 3 active sync /dev/sde2
>>
>> This makes sense to me as far as it goes but I don't see what to do
>> next. As I understand it the four partitions from sda2 to sdd2 would
>> form the array with sde as hot spare. It has been my assumption that if
>> a drive failed that sde would sync and take over. I don't know if this
>> is in fact the case and don't see a path forward. Of course the backups
>> are inadequate.
>
>
> Based on the events and update timestamps, sdd died sometime around Wed
> Sep 4 07:51:50 2013, at which point sde stepped in. It too failed
> shortly after ~ Sun Sep 8 13:25:42 2013. You then ran degraded for over
> a year until sdb also failed ~ Sat Nov 22 13:18:12 2014. You were then
> running doubly-degraded (luckily on non-adjacent members) until this Feb
> 14 when sda was booted out. Leaving only one running drive.
>
> { I wouldn't keep such people around, either. }
>
> Your best bet is to force assembly of the last two working drives to get
> the system running, then take an immediate backup of all critical files.
> Do the forced assembly with the livecd, then do a clean shutdown. You
> should then be able to boot the original OS and take your backup.
>
> Then you need to completely rebuild your system with proper log
> monitoring, array monitoring, and verification of your drives.
>
> Phil
>
>
> --
> "As long as politics is the shadow cast on society by big business,
> the attenuation of the shadow will not change the substance."
>
> -- John Dewey
>
>
>
>
>
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