Re: 5.18: likely useless very preliminary bug report: mdadm raid-6 boot-time assembly failure

[Nix <nix@esperi.org.uk>]

On 22 Jul 2022, Wols Lists spake thusly:

> On 22/07/2022 10:57, Nix wrote:
>> I thought all the work done to assemble raid arrays was done by mdadm?
>> Because that didn't change. Does the kernel md layer also get to say
>> "type wrong, go away"? EW. I'd hope nothing is looking at partition
>> types these days...
>
> As far as I know (which is probably the same as you :-) the kernel knows nothing about the v1 superblock format, so raid assembly
> *must* be done by mdadm.
>
> That's why, despite it being obsolete, people get upset when there's any mention of 0.9 going away, because the kernel DOES
> recognise it and can assemble those arrays.

Right. These are all v1.2, e.g. for one of them:

/dev/md125:
        Version : 1.2
  Creation Time : Mon Apr 10 10:42:31 2017
     Raid Level : raid6
     Array Size : 15391689216 (14678.66 GiB 15761.09 GB)
  Used Dev Size : 5130563072 (4892.89 GiB 5253.70 GB)
   Raid Devices : 5
  Total Devices : 5
    Persistence : Superblock is persistent

    Update Time : Fri Jul 22 15:58:45 2022
          State : active 
 Active Devices : 5
Working Devices : 5
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 512K

           Name : loom:fast  (local to host loom)
           UUID : 4eb6bf4e:7458f1f1:d05bdfe4:6d38ca23
         Events : 51202

    Number   Major   Minor   RaidDevice State
       0       8        3        0      active sync   /dev/sda3
       1       8       19        1      active sync   /dev/sdb3
       2       8       35        2      active sync   /dev/sdc3
       4       8       51        3      active sync   /dev/sdd3
       5       8       83        4      active sync   /dev/sdf3