Ok, this is at least some good news.
It might be as simple as to import your pool.
Just because everything is there twice, doesnt mean it seamlessly switches over.
Dual Controller is not supported in SCALE and your HDs are not double. You can only loose 2 drives out of 24 in a Raidz2
Great that you have a spare unit and great that the disks show up.
zpool import
Does that give you the option to import the pool?
Great - that was to be my next question!
Have you followed @chuck32 suggestion to attempt an import? If so, what happened?
Hi All
So this is what I got from the import command.
root@truenas[~]# zpool import
pool: AEWC DATA
id: 15761599832217586264
state: ONLINE
action: The pool can be imported using its name or numeric identifier.
config:
AEWC DATA ONLINE
raidz3-0 ONLINE
gptid/0d62a66b-50b2-11ed-8eeb-0007430865e0 ONLINE
spare-1 ONLINE
gptid/0f4c2510-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/18e003ae-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0d48af08-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0d6f1818-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0f7b9d20-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/11da9500-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0f5dad8b-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0a38d576-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0d5a6b07-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0f64f409-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/11e508db-50b2-11ed-8eeb-0007430865e0 ONLINE
spare-11 ONLINE
gptid/d2019950-5ae5-11ed-be36-0007430865e0 ONLINE
gptid/187f3844-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0f6f2d4d-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/11d07a82-50b2-11ed-8eeb-0007430865e0 ONLINE
spare-14 ONLINE
gptid/0f52c382-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/18cdc758-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/0d3e1729-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/15518036-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/18e985b5-50b2-11ed-8eeb-0007430865e0 ONLINE
gptid/18
If i go to try and import a pool - Storage>pools>add>import i get as far as selecting a pool, and my pool doesn’t show?
I thought from the above this is online and can be imported using its name? but then the name doesn’t show?
Try Importing via CLI
zpool import "AEWC DATA"
to avoid problems due to the space in the name, or I guess this should work with the numeric ID (haven’t imported that way before).
zpool import 15761599832217586264
Edit: just to clarify, do you see the pool in GUI right now? If so and importing via CLI doesn’t work, try to see if you can export the pool in the GUI.
So, are we getting somewhere?
root@truenas[~]# zpool import “AEWC DATA”
zpool import 15761599832217586264
cannot import ‘AEWC DATA’: I/O error
Recovery is possible, but will result in some data loss.
Returning the pool to its state as of Sat May 4 01:54:22 2024
should correct the problem. Approximately 9 seconds of data
must be discarded, irreversibly. Recovery can be attempted
by executing ‘zpool import -F AEWC DATA’. A scrub of the pool
is strongly recommended after recovery.
Did you run the forced import yet?
It should work after discarding the last 9 seconds of history on the pool.
Looks like you’re going to need to use the F (force) switch and lose some data. Courtesy of an @dan earlier post, I quote "There are two “force” options to ‘zpool import’. -f will import the otherwise-healthy pool if it appears it was last in use on another system. -F (capital F) will attempt to roll back the last n transactions (where n is a constant whose value I don’t know) to try to bring the pool to a mountable state. You can combine -F with -n to do a “dry run” of the force import–it will tell you if it could import your pool that way, but won’t actually import it. That command would look like ‘zpool import -F -n AEWC DATA’. "
So…not sure what has happened.
I typed the recovery option above - zpool import -F AEWC DATA - All i got was
root@truenas[~]# zpool import -F AEWC DATA
cannot import ‘AEWC’: no such pool available
So nothing seemed to be working. it seemed to be constantly looking for AEWC and not AEWC DATA. i tried using the ID number too, and that didn’t recognise.
Then…the pool suddenly appeared, it shows one drive faulted and has resilvered into one of the spare ones.
No idea what or how it worked, or if it was anything i did??
Only thing now is it isn’t showing folders in network as it isn’t recognising any password to access this?
Maybe I wasn’t clear with my post / I also don’t know the correct syntax on top of my head, you have spaces in your pool name. This will terminate the command at AEWC because there’s a space after it will not properly recognize AEWC DATA as the full name, hence I suggested using "AEWC DATA".
It told you by pouting out it didn’t find the pool named AEWC.
It seemed to have worked the post before and apparently (since the pool is there again) seems to have worked now, too. What message did lead you to thinking it didn’t work?
Out of curiosity, zpool status again please 
Not my specialty, maybe the import command screwed up the mount point?
Can you ssh into the machine and do ls / you can then navigate to your pool, should be under /mnt/poolname and check for your files there. Remember the space in the name, use “”.
Then go to your SMB shares or whatever you were using and verify:
When the path is correct you may add a new user to the share, apply permissions recursively and see if you can get to your data.
Your next step should be to figure out a viable backup solution. Personally I’d advise to use your spare unit (if it isn’t too old by now, I haven’t checked the specs) or get another system and create a new NAS with less drives. Keep your current NAS as a backup.
If you import in the cli, you’ll want to export again, and then import in the gui
It’s similar to this:
I haven’t read your whole linked thread in the time obviously. Why is this necessary?
But it gave me an idea to a another explanation: maybe the system dataset got corrupted during tossing the last x seconds, and hence the file share is broken?
You may need to reconfigure the share as I pointed out earlier.
I believe TrueNAS mounts a pool in a non-default location when you import in the GUI.
Thanks! You mean via CLI?
That would also make sense, I already had a hunch it was the mount point. Hitting the bed now, but I’m curious what the answer will be for OP.
Hi Chuck
I tried all of the above, “aewc data” and it all showed the same response as above. When it tried the ID number it just didn’t recognise.
root@truenas[~]# zpool status
pool: AEWC DATA
state: DEGRADED
status: One or more devices are faulted in response to persistent errors.
Sufficient replicas exist for the pool to continue functioning in a
degraded state.
action: Replace the faulted device, or use ‘zpool clear’ to mark the device
repaired.
scan: resilvered 88.7M in 00:07:01 with 0 errors on Mon May 6 14:03:44 2024
config:
NAME STATE READ WRITE CKSUM
AEWC DATA DEGRADED 0 0 0
raidz3-0 DEGRADED 0 0 0
gptid/0d62a66b-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
spare-1 ONLINE 0 0 0
gptid/0f4c2510-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/18e003ae-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0d48af08-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0d6f1818-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0f7b9d20-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/11da9500-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0f5dad8b-50b2-11ed-8eeb-0007430865e0 FAULTED 129 0 0 too many errors
gptid/0a38d576-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0d5a6b07-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0f64f409-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/11e508db-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
spare-11 ONLINE 0 0 0
gptid/d2019950-5ae5-11ed-be36-0007430865e0 ONLINE 0 0 0
gptid/187f3844-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0f6f2d4d-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/11d07a82-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
spare-14 ONLINE 0 0 0
gptid/0f52c382-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/18cdc758-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/0d3e1729-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/15518036-50b2-11ed-8eeb-0007430865e0 ONLINE 0 0 0
gptid/187f3844-50b2-11ed-8eeb-0007430865e0 INUSE currently in use
gptid/18e003ae-50b2-11ed-8eeb-0007430865e0 INUSE currently in use
gptid/18cdc758-50b2-11ed-8eeb-0007430865e0 INUSE currently in use
errors: No known data errors
pool: boot-pool
state: ONLINE
scan: scrub repaired 0B in 00:00:29 with 0 errors on Fri May 3 03:45:29 2024
config:
NAME STATE READ WRITE CKSUM
boot-pool ONLINE 0 0 0
I will need to check on the last bit, im not fully sure what you are suggesting.
If you ever import a pool via CLI make sure you add -o altroot=/mnt to the command.
Follow @Stux advice first, as suspected (and according to @pmh input, the path is now probably different).
Already one eye closed here 
but I would double check that, at a glance it seems like you are already using all your spaces and would need to replace the faulted drive manually now, I do not think you have a spare left and neither is the pool healthy. This requires timely action on your side. Since you are using raidz3 you should have some time left but you’re also using a really wide system.
At least one of those was successful, your pool is imported again
ZFS and CLI are case sensitive as far as I know.
I have only got 24 drives in, there is space for 36, 12 are empty so plenty of room?
I also have 3 spare empty drives in the system to silver to if there was a failure i think, showing 5tb free space.
Many thanks for your help. I will have to look at again tomorrow.