For one, Gnau questions the ability of the Exadata's flash cache to store the huge data sets often crunched by analytics apps. "You have to know exactly what stuff you plan to park there, or get lucky," he said.
That means data will be scattered on several places -- the RAM, the flash and then disk -- all with different access speeds. That will result in dependencies and bottlenecks -- problems that will be exacerbated in multiserver clusters and grids, contended Gnau.
Rather than trying to play traffic cop, Teradata said its approach with its Extreme Performance Appliance 4600 (code-named Blur) is simpler: Use flash-based solid-state disks.
Storing up to 24TB of data, the 4600 connects to the SSDs over the same physical interconnects as hard disks. While theoretically slower than connecting straight to the motherboard via PCIe, it's also an easier-to-handle load-balancing problem, said Gnau, and one that can be addressed using Teradata's virtual storage software.
"This is real direct-attached storage," he said. "We don't use disk controllers; we do all our of data integrity inside our software."
The result, said Gnau is 5 million I/Os per second performance -- fast enough to replace a complex event processing engine or an in-memory database.
Using SSDs throughout won't be cheap, though Gnau declined to comment on that.
Still other, faster options
While Teradata has trashed Oracle's flash-cache approach, it hasn't ruled out using PCIe-based technology down the road.
That's what ParAccel is doing. It's using PCIe to connect to 640GB of flash per server appliance -- about two-thirds more than the Exadata v2 -- to deliver 15X performance boosts, the company said recently.
While ParAccel is reportedly going with Fusion-io, there are other PCIe-based options.
One is an Israeli start-up called PetaScan that has talked to a number of data warehousing firms about its offering.
Scott Yara, president and co-founder of Greenplum, has looked at PetaScan's technology.
"This is absolutely a good direction to go down," Yara said, though he declined to confirm if and when a flash-based appliance might come from Greenplum.
Not everyone is jumping onto the flash bandwagon, however. Netezza said it has tested flash SSDs like Teradata's and found them not worth using.
"Ten times the cost for four times the performance over rotating disk is not a good deal," said Phil Francisco, vice president of marketing at Netezza. But "the jury is still out" on PCIe-based flash, he added.
Eric Lai covers Windows and Linux, desktop applications, databases and business intelligence for Computerworld. Follow Eric on Twitter at @ericylai, send e-mail to elai@computerworld.com or subscribe to Eric's RSS feed .