Explanation/Reference:
B: * Grid disks (the logical disks
that reside on physical cell disks) are created on these flash-based cell disks and the grid disks are assigned to an Automatic Storage Management (ASM) diskgroup. The best practice would be to reserve the same amount of flash on each Exadata cell for flash disks and have the ASM diskgroup spread evenly across the Exadata cells in the configuration just as you would do for regular Exadata grid disks. This will evenly distribute the flash I/O load across the Exadata cells and flash.
Note:
* The Exadata
Storage Server comes with a substantial amount of flash storage. A small amount is allocated for database logging and the remainder will be used for caching user data