Before:
# zpool list sestore6b
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
sestore6b 239T 230T 9.07T - 23% 96% 1.00x ONLINE -
# zfs list sestore6b
NAME USED AVAIL REFER MOUNTPOINT
sestore6b 176T 228G 219K /sestore6b
After Phase 1:
# zpool list sestore6b
NAME SIZE ALLOC FREE EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
sestore6b 348T 230T 118T - 16% 66% 1.00x ONLINE -
# zfs list sestore6b
NAME USED AVAIL REFER MOUNTPOINT
sestore6b 176T 80.7T 219K /sestore6b
Phase 2 will replace 12x 5TB with 12x 12TB and grow it further