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

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

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)

What am I overlooking?