I have a zfs pool that holds my backup. Every disk has only one partition.

~# zpool status backup_pool
  pool: backup_pool
 state: ONLINE
  scan: resilvered 108K in 00:00:00 with 0 errors on Tue Jun 18 13:48:11 2024
config:

        NAME                        STATE     READ WRITE CKSUM
        backup_pool                 ONLINE       0     0     0
          raidz3-0                  ONLINE       0     0     0
            wwn-0x5000c500e4eb728d  ONLINE       0     0     0
            wwn-0x5000c500c2871419  ONLINE       0     0     0
            wwn-0x5000c500c53c108f  ONLINE       0     0     0
            wwn-0x5000c500aa36deaa  ONLINE       0     0     0
            wwn-0x5000c500aa36dbd7  ONLINE       0     0     0
            wwn-0x5000c500e4eb6f87  ONLINE       0     0     0
            wwn-0x5000c500e4eb8122  ONLINE       0     0     0
            wwn-0x5000c500c68c2b61  ONLINE       0     0     0
            wwn-0x5000c500c5f7d53c  ONLINE       0     0     0
            wwn-0x5000c500c715f9a7  ONLINE       0     0     0
            wwn-0x5000c500e4eb6c51  ONLINE       0     0     0
            wwn-0x5000c500c712df17  ONLINE       0     0     0
            wwn-0x5000c500c728ef7a  ONLINE       0     0     0
            wwn-0x5000c500aa36d8a5  ONLINE       0     0     0
            wwn-0x5000c500e8304e87  ONLINE       0     0     0
        spares
          wwn-0x5000c500e4eb7579    AVAIL   

errors: No known data errors

Lately, I noticed there is a high rate of disk failure on my disks.
One thought was zfs is actively using the disk in active raidz pool and causes I/O failure after X months. But spares wouldn’t have I/O, so the failure shouldn’t happen there.

Looking at the pool, I’m not using the disk space to its max capacity.

~# zfs list backup_pool
NAME          USED  AVAIL     REFER  MOUNTPOINT
backup_pool  3.81T  45.6T     3.81T  /backup_pool

Therefore, I can reduce the number of disks in raidz3-0 and put them in as spares.
But

~# zpool offline backup_pool wwn-0x5000c500e8304e87
~# zpool remove backup_pool wwn-0x5000c500e8304e87
cannot remove wwn-0x5000c500e8304e87: operation not supported on this type of pool
~# zpool add backup_pool spare wwn-0x5000c500e8304e87
invalid vdev specification
use '-f' to override the following errors:
/dev/disk/by-id/wwn-0x5000c500e8304e87-part1 is part of active pool 'backup_pool'

Question is: Does ZFS support what I’m trying to do? If so, how to perform it, properly?