JorgeB

As mentioned, many small files will always be slower, this is normal with any OS, it will be the same if you transfer from one Windows PC to another.

If you want to use zfs won the array you don't need the flash drive. Not in the array. Nest release will still require an array device assigned, at least that's the last I heard, but you can already do a full zfs implementation, if like mentioned, you use a flash drive to fulfill the array device requirement.

The issue is not using zfs for all, you can also use zfs for the array, but for now, at least one device must be assigned to the array if you want to only use pools, an old flash drive will do it.

Copying many small files will always be slower than large ones, but you should see a nice boost if you set the share to exclusive mode, or use a disk share.

Run the make_bootable.bat as admin, syslinux is not needed for UEFI boot, but it is for legacy, and make sure the flash drive is still the first boot device.

The SMART report for that disk, this part: SMART Extended Self-test Log Version: 1 (1 sectors) Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error # 1 Extended offline Completed without error 00% 58305 -

The pool is using the single profile, i.e., not redundant, and it will only mount if both devices are available, you can convert to raid1 to make it redundant.

Check filesystem on disk4, run without -n and if it asks for it, use -L.

Yes, if the drive is encrypted, and still in maintenance mode, you need to use: /dev/mapper/mdXp1

md device should not be busy in maintenance mode, try rebooting

Those appear to be the same diags as before, would need current ones, with the pool mounted.

IMHO it can be considered a bug regarding the errors logged, which are misleading, the behavior itself would be expected, i.e., if the share is set to use one pool, the mover won't move any data from the same share in a different pool.

If it's configured as a redundant pool yes, you can post new diags to confirm.

Post the output of btrfs fi show

Once a disk gets disabled it needs to be rebuilt, but first post new diags to see if the ATA errors are gone.