Consider these points when planning for disk space growth:
Less administration time is required to configure disks during initial configuration than to add them while the system is in service.
Leaving empty slots in the multihost disk expansion units during initial configuration allows you to add disks easily later.
When your site needs additional disk expansion units, you might have to reconfigure your data to prevent mirroring within a single disk expansion unit. Therefore, if all the existing disk expansion units are full, the easiest way to add disk expansion units without reorganizing data is to add them in pairs.