Exadata Flash Hardware
Now that we have thoroughly reviewed Flash SSD technology and the Database Flash Cache, let’s look at how Flash SSD is incorporated into the Exadata architecture. In an Exadata system, Flash SSD is contained in the Storage Cells only. There is no SSD configured within the Compute Nodes.
Each Storage Cell contains four PCIe Flash SSD drives. The exact configuration depends on the Exadata version:
- On an X2 system, each cell contains four 96GB Sun F20 SLC PCI Flash cards. That’s 384GB total per Storage Cell for a total of 5.2TB of Flash in a full Exadata rack.
- On an X3 system, each cell contains four 400GB Sun F40 MLC PCI Flash cards. That is 1.6TB of Flash per cell and a total of 22.4TB of Flash for a full Exadata rack.
- On an X4 system, each cell contains four 800GB Sun F80 MLC PCI Flash cards. That’s 3.2TB of Flash per cell and a total of 44.8TB of Flash for a full Exadata rack!
Note that the increase in capacity between X-2, X-3, and X-4 has been achieved not by adding more Flash SSD cards, but by increasing the capacity of each drive.
Also note that the increase in capacity in X-3 was achieved primarily by moving from SLC to MLC cards. While it’s true that SLC is inherently more durable and offers lower latencies than MLC, it’s also true that in the years since the F20 was introduced MLC technology has improved significantly. Oracle claims the MLC F40 cards, shown in Figure 15.8, actually have twice the raw throughput of the SLC F20 cards.
Figure 15.8 Oracle Sun F40 PCIe Flash SSD