William Morgan [off-list ref] 于2020年3月6日周五 下午10:35写道：

On Thu, Mar 5, 2020 at 11:22 AM Wols Lists [off-list ref] wrote:

quoted

On 05/03/20 14:53, Jinpu Wang wrote:

quoted

"mdadm /dev/md0 -a /dev/sdl1"  should work for you to add the disk
back to array, maybe you can check first with "mdadm -E /dev/sdl1" to
make sure.

Or better, --re-add or whatever the option is. If it can find the
relevant data in the superblock, like bitmap or journal or whatever, it
will just bring the disk up-to-date. If it can't, it functions just like
add, so you've lost nothing but might gain a lot.

Cheers,
Wol

I tried re-add and I get the following error:

bill@bill-desk:~$ sudo mdadm /dev/md0 --re-add /dev/sdl1
mdadm: Cannot open /dev/sdl1: Device or resource busy

sdl is not mounted, and it doesn't seem to be a device mapper issue:

bill@bill-desk:~$ sudo dmsetup table
No devices found

This is strange.
have you checked if any other process is using sdl1?
"sudo lsof /dev/sdl1"

Here is the current state of sdl:

bill@bill-desk:~$ sudo mdadm -E /dev/sdl1
/dev/sdl1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x9
     Array UUID : 06ad8de5:3a7a15ad:88116f44:fcdee150
           Name : bill-desk:0  (local to host bill-desk)
  Creation Time : Sat Sep 22 19:10:10 2018
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 15627786240 (7451.91 GiB 8001.43 GB)
     Array Size : 23441679360 (22355.73 GiB 24004.28 GB)
    Data Offset : 264192 sectors
   Super Offset : 8 sectors
   Unused Space : before=264112 sectors, after=0 sectors
          State : clean
    Device UUID : 8c628aed:802a5dc8:9d8a8910:9794ec02

Internal Bitmap : 8 sectors from superblock
    Update Time : Mon Mar  2 17:41:32 2020
  Bad Block Log : 512 entries available at offset 40 sectors - bad
blocks present.
       Checksum : 7b89f1e6 - correct
         Events : 10749

         Layout : left-symmetric
     Chunk Size : 64K

   Device Role : spare
   Array State : AAA. ('A' == active, '.' == missing, 'R' == replacing)

The metadata looks fine.
If no one holds the disk, maybe last resort to zero out the metadata
and add the disk back, maybe first try David's suggestion, stop array
first and try re-add.