Made the mistake of editing my zfs pools from the command line on FreeNas 8.0.2. Ended up discovering something. FreeNas uses a database to keep track of things like volumes and the like. Manually messing with things from the command line throws things out of whack to the point that you have to go in and manually repair them. So the procedure goes like this.
ssh into freenas. su to root. Then sqlite3 /data/freenas-v1.db
Then list the tables
account_bsdgroupmembership account_bsdgroups account_bsdusers auth_group auth_group_permissions auth_message auth_permission auth_user auth_user_groups auth_user_user_permissions django_content_type django_session network_alias network_globalconfiguration network_interfaces network_lagginterface network_lagginterfacemembers network_staticroute network_vlan services_activedirectory services_afp services_cifs services_dynamicdns services_ftp services_iscsitarget services_iscsitargetauthcredential services_iscsitargetauthorizedinitiator services_iscsitargetextent services_iscsitargetglobalconfiguration services_iscsitargetportal services_iscsitargettoextent services_ldap services_nfs services_rsyncd services_rsyncmod services_services services_smart services_snmp services_ssh services_tftp services_ups sharing_afp_share sharing_cifs_share sharing_nfs_share south_migrationhistory storage_disk storage_diskgroup storage_mountpoint storage_replication storage_replremote storage_task storage_volume system_advanced system_cronjob system_email system_rsync system_settings system_smarttest system_ssl Then sqlite> select id, disk_description from storage_disk
Output for me was
1|Member of tank raidz 2|Member of tank raidz 3|Member of tank raidz 4|Member of tank raidz 5|Member of BigWest stripe 6|Member of BigWest stripe1
Now, delete your mistakes.
sqlite> delete from storage_disk where id=5;
sqlite> delete from storage_disk where id=6;
Now do the same for storage_volume and storage_diskgroup
I’m sure there are other ways you can make FreeNas unhappy, so maybe this little hint will help with that too.