Where iSCSI fits in

Just as storage vendors start to sell SAS and 2.5-inch drives, they’re also pitching iSCSI. But iSCSI isn’t really a form of SCSI, nor does it have any real relationship with the SCSI technology evolution.

iSCSI is actually an external interface to connect storage systems, similar to FC (Fibre Channel) or Infiniband. An iSCSI connection uses the Ethernet as the data transport and packages the storage management commands for delivery via TCP/IP. But an iSCSI connection works equally with ATA, SCSI, and FC storage systems. (FC is both an external connection technology and a specific drive technology, but similar to iSCSI, it connects any type of drive system.)

That means enterprises should evaluate the merits of iSCSI -- essentially a cheaper SAN connection method with slower performance -- separately from those of SAS and 2.5-inch drives. “The primary advantage is lower cost of connectivity,” says Jay Krone, director of Clariion product marketing at EMC.

“There’s a school of thinking in the low-end server market that iSCSI would be a cheaper way to do [direct-attached] storage,” says Harry Mason, director of industry marketing at LSI Logic. But Mason’s not convinced. “SAS took all the wind out of iSCSI’s sails in that kind of implementation because it gives all the predictability and bandwidth without having to build a new environment.” Mason, citing offerings from companies such as LeftHand Networks and EqualLogic, does see iSCSI as an appropriate SAN alternative for low-performance environments such as small businesses and for linking isolated SANs.