A big, big file system
Still, another means to connect the SAN and NAS worlds is through technology that essentially creates a file system for SANs. For instance, IBM's SAN File System -- launched last year -- is designed to tie together servers in multiple locations over an Internet Protocol network and then allow the SAN to look and behave like a local file system, no matter where the data resides. Software keeps track of descriptive information, or "metadata," such as physical locations, file sizes and access permissions, that accompanies the actual content within the files, IBM said.
SAN File System is part of IBM's broader "on demand" computing initiative, which aims in part to provide information technology systems that smoothly handle spikes in usage. Sun Microsystems and Hewlett-Packard are working on related efforts.
IBM's SAN File System is more complicated to put in place than a typical NAS box. SAN File System software runs on metadata servers dedicated to it. In addition, software has to be installed on other servers using the system. But Big Blue said that the product can manage petabytes of data -- one petabyte is equivalent to a million and a half CDs, IBM said.
"This is the ultimate of that (NAS-SAN) convergence," said Jeff Barnett, manager of marketing strategy for IBM's storage software unit. "A single NAS box is not going to scale to petabytes of data."
Perhaps not, but BlueArc said its new Titan product allows for up to 12 units to be clustered together for a total system capacity of 3 petabytes. Key to making its NAS products act like a SAN is the use of programmable silicon chips, according the company. BlueArc integrates a number of tasks usually reserved for software -- such as protocols and network services -- into so-called field-programmable gate arrays. That provides a speed boost that allows customers to run database programs or other applications that frequently use a block-level approach without a performance penalty, the company said.
"The distinction between SAN and NAS is blurred to some degree," said Geoff Barrall, chief technical officer at BlueArc.
The new Titan product has an architecture that will permit businesses to upgrade the speed of the product from 5gbps to an eventual 20gbps. What's more, the Titan supports larger file systems -- up to 256 terabytes in a single file system -- which can make for easier storage management, BlueArc said.
Two other smaller players in the storage world, Isilon Systems and Panasas, also have NAS products that are designed to let companies easily increase data capacity.
Although the NAS-SAN crossover has begun, the trend will increase with the emergence of iSCSI, Cox said. iSCSI is an interface technology that allows SANs to be built using less-expensive Ethernet networks. Another possible catalyst is the evolution of Ethernet bandwidth, which is expected to increase to 10gbps within the next couple of years, Cox said.
"Then you've got Ethernet on the same playing field as Fibre Channel," he said. "That's when all that gets real interesting."
