Re: mdadm --detail works, mdadm --stop says "does not appear to be an md device"

[Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>]

On Fri, 17 Mar 2023 10:38:10 -0700
Marc MERLIN <marc@merlins.org> wrote:

> gargamel:~# cat /proc/mdstat 
> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
> [multipath] md6 : active raid5 sdn1[3](F) sdt1[0](F) sds1[1](F) sdq1[2](F)
>       23441547264 blocks super 1.2 level 5, 512k chunk, algorithm 2 [5/0]
> [_____] gargamel:~# mdadm --stop /dev/md6
> mdadm: /dev/md6 does not appear to be an md device
> gargamel:~# mdadm --detail /dev/md6
> /dev/md6:
>            Version : 1.2
>      Creation Time : Wed Jul  8 10:09:21 2020
>         Raid Level : raid5
>         Array Size : 23441547264 (22355.60 GiB 24004.14 GB)
>      Used Dev Size : 5860386816 (5588.90 GiB 6001.04 GB)
>       Raid Devices : 5
>      Total Devices : 4
>        Persistence : Superblock is persistent
> 
>        Update Time : Fri Mar 17 09:17:28 2023
>              State : clean, FAILED 
>     Active Devices : 0
>     Failed Devices : 4
>      Spare Devices : 0
> 
>             Layout : left-symmetric
>         Chunk Size : 512K
> 
> Consistency Policy : ppl
> 
>     Number   Major   Minor   RaidDevice State
>        -       0        0        0      removed
>        -       0        0        1      removed
>        -       0        0        2      removed
>        -       0        0        3      removed
>        -       0        0        4      removed
> 
> 
> How do I clear this without a reboot?
> 
> gargamel:~# uname -r
> 5.19.7
> 
> 

Hi,
mdadm is unable to complete this task because it cannot ensure that it is safe
to stop the array. It cannot open the array with O_EXCL.
If it is mounted then it may hang if filesystem needs to flush some data.

Please, try umount the array if it mounted somewhere and then try:

# echo inactive > /sys/block/md6/md/array_state
# echo clear > /sys/block/md6/md/array_state

Thanks,
Mariusz