by DAVE SIMPSON
This month, 3ware Inc. began shipments of a RAID array that allows the transmission of block-level SCSI data over Gigabit Ethernet LANs or subnet SANs. Mountain View, CA-based 3ware is best-known as a manufacturer of ATA/IDE RAID controllers.
"3ware is first to market with an iSCSI disk array-a block-level disk device that connects to Ethernet," says Steve Duplessie, an analyst with the Enterprise Storage Group. "This is the first of many iSCSI products to come next year, so 3ware is clearly on the front end of the movement."
3ware's Network Storage Unit (NSU) is based on "iSCSI-ready" technology that allows the transmission of SCSI over the full TCP/IP protocol stack. When the iSCSI specification is completed some time next year, 3ware plans to make its technology compatible with the standard and upgrade its existing customers at no cost. The iSCSI spec is currently under development in the Internet Engineering Task Force (IETF).
"It's our best approximation of what iSCSI will eventually become," says John "Beau" Vrolyk, president and CEO of 3ware. "We're effectively layering a fourth-level protocol on top of TCP/IP, much the way HTTP is layered on top of TCP/IP." iSCSI is essentially a protocol that sits on top of the TCP, IP, and Ethernet layers. TCP handles functions such as retransmission, re-routing, and packet ordering.
3ware's Network Storage Unit (NSU) can attach directly to an Ethernet switch and allows block-level storage to travel over standard TCP/IP networks.
Running block-level SCSI over standard TCP/IP networks provides end users with an alternative to Fibre Channel-based storage area networks (SANs) and network-attached storage (NAS). NAS transfers data at the file level, as opposed to the block level. "NSU provides an alternative to expensive and proprietary Fibre Channel storage technologies," says Vrolyk.
However, Vrolyk is quick to point out that storage over TCP/IP does not provide the performance levels available with Fibre Channel, which provides a theoretical maximum transfer rate of 100MBps-typically, 90MBps in best-case scenarios. "Fibre Channel is a more efficient protocol, so it gets more of the physical bandwidth delivered at the application layer than does
TCP/IP on Gigabit Ethernet," Vrolyk explains. In initial testing, 3ware achieved 65MBps, although Vrolyk says real-life rates could be considerably less.
On the plus side, however, running block-level storage over standard TCP/IP networks can provide considerable advantages, including
- Easier management;
- Use of existing infrastructure (as op-posed to building a separate network with a separate protocol set);
- Significantly lower overall cost, including per-port costs for switches (compared to Fibre Channel); and
- No need to hire additional personnel to deploy and manage Fibre Channel SANs.
Pricing for the NSU, which includes 3ware's Escalade ATA/IDE controllers, ranges from $29,000 for a 240GB configuration to $49,000 for a 600GB version. All configurations are based on ATA/IDE drives. Host drivers are available for Windows 2000, NT, and Linux.
Separately, 3ware announced benchmark results for its Escalade controllers. National Technical Systems Inc. (www.ntscorp.com), an independent testing organization, clocked the Escalade controllers at 164MBps in sequential reads and 73MBps in sequential writes. In both instances, the ATA/100 controllers significantly outperformed more-expensive Ultra160 SCSI controllers from Adaptec and Mylex. The tests used Intel's IOMeter benchmark suite.
The Escalade controllers are based on 3ware's DiskSwitch packet-switching technology, which allows the controller to access multiple drives simultaneously, as opposed to the shared-bus architecture of SCSI. 3ware claims transfer rates of more than 185MBps in a RAID 0 configuration and 163MBps in a RAID 10 array.
3ware recently received $43 million in equity funding from an investment group that includes Quantum Technology Ventures and Veritas Software.