What's taking up space on this empty zpool?

[Fish]

I'm in the process of decommissioning a ZFS pool. I have moved and deleted all datasets and shapshots, but it still seems as though ~150MB is in use. Is this just due to metadata for the pool? How can I see what is being stored and whether it maters?

Code:

root@freenas:~ # zpool list
NAME           SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOT
vol1          3.62T   143M  3.62T        -         -     8%     0%  1.00x    ONLINE  /mnt
root@freenas:~ # zfs list -t snapshot | grep -i vol1
root@freenas:~ #

 

[sretalla]

ls -l /mnt/vol1

If you find nothing there and as you saw there are no snapshots, all that leaves is metadata.