Early this week flash memory vendor Spansion announced its EcoRAM solution, a product that lets you cram 512 GB of flash memory that presents as RAM to an Opteron-based system. The solution offers the same read performance as DRAM in much larger capacities with better per-GB reliability, and doesn’t increase power consumption. Sounds pretty good, but there are some things you should think about before you rush out and make a buy.
The two major kinds of flash memory are NOR and NAND; both are non-volatile. Most of the flash-based solid state disks (SSDs) that all the kids are talking about these days are NAND-based. NOR has faster read speed than NAND, but is slower on write and erase. NOR also requires a larger design feature size, which means it will probably always be more expensive per gigabyte than NAND flash. Both NOR and NAND have write degradation issues, but NOR does not have the read wear problems that NAND does. NOR is used for code storage in devices like cell phones and PDAs, where density isn’t a huge concern but the fastest possible load time is.
Some in the memory industry anticipate that NOR will become obsolete in favor of other technologies such as Ferroelectric RAM and Phase Change Memory which offer better cost structure and better performance than NOR Flash, but these changes are several years out. In the meantime, Spansion has been looking for other applications for their NOR memory, and they believe they’ve found one with their EcoRAM product.
NAND-based storage solutions from companies like Sun and Fusion-IO typically slot into systems where they masquerade as disk (really fast block IO devices). EcoRAM presents itself a main memory to the CPUs. The product is based on HyperTransport, and so only works in AMD-based systems. A special hardware device, the Spansion EcoRAM accelerator, plugs into one of the CPU slots on a node board (for four socket boards you can put an accelerator into each of 2 sockets). The EcoRAM memory sticks then go into that socket’s DIMM slots. The accelerator takes advantage of AMD’s Torrenza interface to present the flash memory as RAM to the other CPU(s) on the node. Each EcoRAM accelerator socket manages up to 8 32 GB flash memory sticks, for a total of 256 GB (you can put up to 512 GB of EcoRAM in a 4 node board with two accelerators).
EcoRAM claims the reliability of each 32 GB stick is the same as a 4 GB stick of DRAM, and that they have the same 10 watt power draw. You won’t be able to buy it yourself and put it into your cluster at the house. Spansion’s Jan Silverman, Vice President of the Server & Storage business unit, explained to me that the reason for this is that, while AMD’s Torrenza specification is clear and complete, the individual node board manufacturers’ products do not uniformly support the protocol. Boards need to be evaluated on a per product basis to ensure that they will recognize the EcoRAM when it’s loaded into a system.
Silverman explains that the product is positioned for read-dominant applications like visualization, search, social networking, and data intensive computing. Something to keep in mind is that because of the slower-than-DRAM write performance, applications for EcoRAM really need to keep a single working set in memory and perform multiple operations on it before moving on.
Spansion’s go-to-market partners today are Appro in the HPC market, and a company called Virident which focuses on scale out solutions for datacenters where _memcached_ and MySQL are big parts of the business (i.e., internet applications providers). Maria McLaughlin, Appro’s director of marketing, said in an email that “Appro will use the Spansion EcoRam memory accelerator for customized products targeting Oil and Gas Visualization and Life Sciences.” She also indicated that they anticipate that customers will add EcoRAM on part of the servers in a cluster to address specific memory-intensive requirements. As of this writing pricing is not available.