Disable --write-behind for existing array

[Jens Stutte <jens@xxxxxxxxxxxxxxxxxx>]

Hello!

I have a RAID1 array made of two identical SSD. The array historically 
contained spinning disks, and I find the following configuration on both 
devices now:

mdadm -X /dev/sdb1
        Filename : /dev/sdb1
           Magic : xxx
         Version : 4
            UUID : xxx
          Events : 32761
  Events Cleared : 32761
           State : OK
       Chunksize : 64 MB
          Daemon : 5s flush period
      Write Mode : Allow write behind, max 4096
       Sync Size : 1953381440 (1862.89 GiB 2000.26 GB)
          Bitmap : 29807 bits (chunks), 1 dirty (0.0%)
mdadm -X /dev/sdc1
        Filename : /dev/sdc1
           Magic : xxx
         Version : 4
            UUID : xxx
          Events : 32761
  Events Cleared : 32761
           State : OK
       Chunksize : 64 MB
          Daemon : 5s flush period
      Write Mode : Allow write behind, max 4096
       Sync Size : 1953381440 (1862.89 GiB 2000.26 GB)
          Bitmap : 29807 bits (chunks), 1 dirty (0.0%)

I assume, it is not very meaningful to have --write-behind active on 
both devices. Actually I would want to remove this configuration for 
both, assuming there is no reason to keep it with two SSD. But a:

mdadm /dev/md0 --fail /dev/sdb1
mdadm /dev/md0 --remove /dev/sdb1
mdadm /dev/md0 --re-add --readwrite /dev/sdb1

did not do the trick and I cannot find any instructions on how to 
disable it on an existing array.

Thanks for any help!

Jens