The VBNs used by each disk are "fixed" in the RAID group so, if a disk is replaced with a bigger one, the amount of VBNs will remain. The empty space in the bigger drive won't be used by WAFL for new ...The VBNs used by each disk are "fixed" in the RAID group so, if a disk is replaced with a bigger one, the amount of VBNs will remain. The empty space in the bigger drive won't be used by WAFL for new VBNs. The aggregate with mixed drives should be destroyed and recreated again with the correct ones. How does Data ONTAP select spares for aggregate creation, aggregate addition and failed disk replacement? How to reduce the number of data disks in an Aggregate / Volume / RAID group