The Write Cache (Logzilla) is in the JBOD, the Read Caches (Readzilla) are in the storage heads. See: http://docs.oracle.com/cd/E26765_01/html/E26399/maintenance__hardware__overview__7320.html#scrolltoc
Thanks for the reply. I see you are pointing to the physical 'read' hardware in the storage head or readzilla. I believe this is where L2ARC storage is maintained. My question is about the Adaptive Replacement Cache (ARC). I am confused about where this and the ghost lists are maintained. References in the various blogs talk about main memory/system memory, which memory is this - the memory in the server node or the memory in the storage head - say the ZFS 7320 Storage as a standalone device or the ZFS 7320 Storage Appliance embedded in an Exalogic.