I'm getting the feeling that "in-memory database" will become redundant in the next few years.
SAP's HANA used to be the first thing that came to mind when the subject arose, but others are getting in the game. Oracle released its Exadata X3
machine at OpenWorld on Sept. 30, which will have 4 TB of DRAM and 22 TB of flash memory capacity per storage node. But data compression technology the company has developed will apparently allow for 10x data compression, allowing a business to store a staggering 220 TB on the solid state drives (assuming the data itself is of the readily compressible kind).
With PCI-e drivers that guide the "hot" data to the DRAM and the "coldest: to spinning disk that can hold up to 5PB, it seems like Oracle has all their bases covered. But this article has a quote from Ellison implying that flash is going to become the de facto standard for these sorts of database machines ("You virtually never use your disk drives").
Oracle hasn't released the read/write speeds for the X3, but I'm curious to see how quickly the compressed data stored in on the flash drives can be accessed. If Oracle does well on that front, their product is going to be very competitive.