So, if I would wonder what is the purpose of this almost "hidden" feature called flash cache and were this came from (also see my post Oracle RDBMS 11gR2 – Flash Cache), now I know. I didn’t have the chance to follow Mr. Ellison’s launch event, but reading Alex Gorbatchev’s blog post on the Pythian web site Unveiling the OLTP Oracle Database Machine & Exadata v2 is enough explanation in the "why" and "how". Flash cache is one of the pillars that make the synergy with the Sun Exadata machine.

As Alex stated:

Exadata Storage Servers

Storage Servers are based on Sun Fire X4275. Again top of the shelf Intel Xeon 5500 Nehalem processors.

Capacity increased — SAS disks are 600 GB (+33%) and SATA disks are 2 TB which doubles what ODBM v1 offered. We all know that big disks are bad but that’s where Sun FlashWire technology comes into play with flash cache on the controllers (5+TB for the full ODBM).

This is what Ellison said about Flash cache:

“These are not Flash disks. Make no mistake — these are no Flash disks. This is a memory hierarchy made up of DRAM in our database servers and Flash in our storage servers with very sophisticated algorithms, not simple LRU — we know for doing a More >