a reboot solved the nvd0 issue

1 - the messages

Aug  3 15:06:02 knew kernel: nvme0: Resetting controller due to a timeout.
Aug  3 15:06:02 knew kernel: nvme0: resetting controller
Aug  3 15:06:32 knew kernel: nvme0: controller ready did not become 0 within 30500 ms
Aug  3 15:06:32 knew kernel: nvme0: failing queued i/o
Aug  3 15:06:32 knew kernel: nvme0: IDENTIFY (06) sqid:0 cid:0 nsid:0 cdw10:00000001 cdw11:00000000
Aug  3 15:06:32 knew kernel: nvme0: ABORTED - BY REQUEST (00/07) sqid:0 cid:0 cdw0:0
Aug  3 15:06:32 knew kernel: nvme0: failing outstanding i/o
Aug  3 15:06:32 knew kernel: nvme0: READ sqid:2 cid:123 nsid:1 lba:250153507 len:5
Aug  3 15:06:32 knew kernel: nvme0: ABORTED - BY REQUEST (00/07) sqid:2 cid:123 cdw0:0
Aug  3 15:06:32 knew kernel: nvme0: failing outstanding i/o
Aug  3 15:06:32 knew kernel: nvme0: WRITE sqid:3 cid:118 nsid:1 lba:454009346 len:1
Aug  3 15:06:32 knew kernel: nvme0: ABORTED - BY REQUEST (00/07) sqid:3 cid:118 cdw0:0
Aug  3 15:06:32 knew kernel: nvme0: failing outstanding i/o
Aug  3 15:06:32 knew kernel: nvme0: WRITE sqid:4 cid:122 nsid:1 lba:454009345 len:1
Aug  3 15:06:32 knew kernel: nvme0: ABORTED - BY REQUEST (00/07) sqid:4 cid:122 cdw0:0
Aug  3 15:06:32 knew kernel: nvd0: detached

2 - zpool status

[dan@knew:~] $ zpool status nvd
  pool: nvd
 state: ONLINE
status: One or more devices has experienced an unrecoverable error.  An
	attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
	using 'zpool clear' or replace the device with 'zpool replace'.
   see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-9P
  scan: scrub repaired 0B in 00:05:09 with 0 errors on Thu Jul 29 04:47:52 2021
config:

	NAME        STATE     READ WRITE CKSUM
	nvd         ONLINE       0     0     0
	  mirror-0  ONLINE       0     0     0
	    nvd0p1  ONLINE       0    57     0
	    nvd1p1  ONLINE       0     0     0

errors: No known data errors
[dan@knew:~] $ 

3 - zpool

[dan@knew:~] $ zpool list nvd
NAME   SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
nvd    222G  23.9G   198G        -         -    45%    10%  1.00x    ONLINE  -

4 - present, but not visible?

zpool status says nvd0 is still there, but it's not in /dev

[dan@knew:~] $ ls -l /dev/nvd*
crw-r-----  1 root  operator  0x76 Jul  1 22:09 /dev/nvd1
crw-r-----  1 root  operator  0x77 Jul  1 22:09 /dev/nvd1p1