Dataram - XcelaSAN - SAN Accleration appliance

Dataram Corp.'s XcelaSAN is a new storage-area network (SAN) acceleration appliance that uses Flash and DRAM memory to cache active blocks for improved performance; it can also front any disk array without requiring changes to the storage or server environment.

XcelaSAN is a caching appliance that sits between a Fibre Channel (FC) switch and storage array. XcelaSAN automatically brings the most frequently used blocks of data in an FC SAN into DRAM and then NAND to speed performance. It works with any vendor's FC SAN, according to Dataram chief technologist Jason Caulkins. Unlike disk array-based solid-state drives (SSDs), the XcelaSAN isn't intended to be persistent storage. The appliance moves data to back-end hard disk drives.

The product is the first NAND product the memory controller maker has rolled out, although Caulkins said the 42-year-old company designed a kind of proto-SSD with a disk drive interface in 1976.

After selling main memory only for approximately three decades, Dataram acquired a company called Cenatek Inc. in 2008. Cenatek designed, built, manufactured and sold PCI-based solid-state drives, Caulkins said, and began devising a new product to compete in the growing solid-state storage market.

XcelaSAN is the result of that acquisition, combining Cenatek's standalone direct-attach SSD IP with Dataram's memory controllers and DRAM into a 2U network device. The product holds 128 GB of RAM cache and 360 GB of Flash, and can be clustered into high-availability pairs and stacked for capacity scaling. Each appliance costs $65,000. Dataram claims the device can perform at 450,000 IOPS or 3 GBps throughput.

It's similar in architecture to Gear6's NFS read caching device, but supports block storage and write caching as well. Another similar product is NetApp Inc.'sFlexCache, which is also focused on NFS and NetApp storage, although it can theoretically be combined with NetApp's V-Series storage virtualization gateway to front heterogeneous storage.

Caulkins argued that Dataram's block-based approach, combined with a caching appliance rather than array-based SSDs, is the most efficient use of Flash. EMC Corp. and others argue that the presence of an SSD makes the entire network loop between server and storage array faster, while Fusion-io Inc. takes another tack claiming Flash make the most sense as close to the server bus as possible.

"It's not cost-effective to put all of your data on SSDs," Caulkins said. "It's better to be able to immediately impact performance without changing files, moving data or figuring out what to put on the SSD."