thanks heargp and peasent for your support,
the situation it's clear but for now i cannot operate in this way because i don't have many disks but only a primary disk, a secondary disk (on witch exist a zfs pool) and an external hd.
So this is the plan i have in mind according with all of your advices and tips, tell me if it can be a TEMPORANY patch for that situation :
1) Move all the content of the
secondary disk to the
external usb drive;
2) Expand the space of the root pool on the primary disk with
zpool add command
3) Once more space has been added to the root pool, set a reservation for the root pool
Question_1) Can this plan be good enough as temporany solution?
Question_2) Between 1 and 2, have i to eliminate the pool i have setted on secondary disk?
thanks to all