Is there any information on replacing drives from these subpools with smaller drives? Appreciate the help.

ZFS doesn't allow that, you would need to remove and recreate the subpools, if using mirrors, removing those is not allowed with RAIDZ.

Thanks for the quick response JorgeB, from a previous post I thought removing subpools of dedup and special was not possible? Am I understanding that I actaully can remove those two specific types of sub pools, if they are not mirrors? This is the current layout of the pool.

NAME               STATE     READ WRITE CKSUM
	dumbpool           ONLINE       0     0     0
	  raidz1-0         ONLINE       0     0     0
	    /dev/sda1      ONLINE       0     0     0
	    /dev/sdb1      ONLINE       0     0     0
	    /dev/sdc1      ONLINE       0     0     0
	  raidz1-1         ONLINE       0     0     0
	    /dev/sdg1      ONLINE       0     0     0
	    /dev/sdh1      ONLINE       0     0     0
	    /dev/sdi1      ONLINE       0     0     0
	  raidz1-6         ONLINE       0     0     0
	    /dev/sdd1      ONLINE       0     0     0
	    /dev/sde1      ONLINE       0     0     0
	    /dev/sdf1      ONLINE       0     0     0
	dedup
	  mirror-5         ONLINE       0     0     0
	    /dev/sdj1      ONLINE       0     0     0
	    /dev/sdl1      ONLINE       0     0     0
	special
	  mirror-3         ONLINE       0     0     0
	    /dev/sdn1      ONLINE       0     0    18
	    /dev/sdk1      ONLINE       0     0    18
	logs
	  /dev/nvme8n1p1   ONLINE       0     0     0
	cache
	  /dev/nvme18n1p1  ONLINE       0     0     0

13 hours ago, bracco said:

from a previous post I thought removing subpools of dedup and special was not possible?

It's possible with mirrors only, not raidz, your pool has raidz vdevs, so not possible.

While I never tested this, it may be possible, if you have extra SATA ports, to add a new vdev with the smaller devices to the existing special and dedup vdevs, then remove the other vdev (using the CLI), I can test this later to confirm if you like.

Thank your JorgeB, that would be amazing if you can verify if that will work. I can make spare ports by removing unallocated drives if it is indeed possible. If you are able to share the terminal commands that would be icing, I am not well schooled in the CLI.

Just did a test and it's not possible. With RAIDZ vdevs in the pool, the zpool remove command is completely blocked, so even after adding a new vdev to special or dedup, it still doesn't allow you to remove the other one, since the new devices are smaller, and you cannot also do a replacement. I'm afraid the only way would be to back up and recreate the pool.

Thank you for giving it a try JorgeB! Appreciate your assistance.