NetApp
Storage > Aggregates : Managing aggregates : Upgrading to a 64-bit aggregate

Upgrading to a 64-bit aggregate
In storage systems running Data ONTAP 8.1 and later, you can upgrade a 32-bit aggregate to a 64-bit aggregate when you add disks to a 32-bit aggregate and the size of the aggregate crosses 16 TB.
Steps 
1.
From the Home tab, double-click the appropriate storage system.
2.
In the navigation pane, click Storage > Aggregates.
3.
Select the 32-bit aggregate whose size you want to increase and click Add Disks.
4.
Select one or more disks and click Add.
5.
Select the confirmation check box and click Add.
This starts the Upgrade to 64 bit aggregate Wizard for upgrading the 32-bit aggregate.
6.
Type or select information as requested by the wizard.
7.
Confirm the details and click Finish to complete the wizard.