Christmas comes early for IP storage: iSCSI achieves wire-speed a year ahead of time.
Alacritech and Nishan connected a server with an Alacritech Server and Storage Accelerator network interface card (NIC) to a Nishan IP Storage switch. The test data moved over Gigabit Ethernet to a Fibre Channel SAN containing a Hitachi Freedom Storage disk subsystem. Alacritech's chip maximized the sustained rate of iSCSI data at over 219MB/sec with less than eight percent CPU utilization, while the Nishan switch provided wire-speed conversion from iSCSI to the HDS storage system. This equals 1GB Fibre Channel speeds.
iSCSI is the most promising protocol for achieving high-speed IP storage requirements. Although IP is a stable and widely used technology, network bottlenecks have precluded the fast speeds that storage area networking requires. In theory, iSCSI would allow Fibre Channel-like speeds over existing IP networks, which would allow storage vendors and administrators to remotely connect SAN islands over Ethernet networks, and to construct IP SANs. This would leverage existing IP technology to eliminate the provisioning and management challenges of administrating both Ethernet and Fibre Channel networks. These challenges have stymied widespread SAN deployment. IP-based storage networking leverages existing IT staff, knowledge, and Ethernet networking standards and widely promises to bring storage networking into the mainstream.
The iSCSI standard works with common protocols by mapping SCSI to TCP/IP, which enables SCSI storage controllers, disk subsystems, and tape libraries to attach directly to IP networks. One of the development issues around iSCSI is that the TCP/IP protocol demands a significant portion of the host CPU's resources, which slows down data movement considerably. To circumvent this, iSCSI research involves offloading protocol stack processing tasks to other devices or layers. One approach is processing TCP/IP and SCSI protocol stacks in the physical layer using host bus adapters (HBA) and/or network interface cards (NIC). Alacritech's SLIC (session-layer interface card) technology splits the TCP stack in two, so it processes data movement in hardware, and control tasks in software. With the entire command stack operating above iSCSI, data processing is significantly accelerated.
Alacritech's IS-NICs use a microchip ASIC (application-specific integrated circuit) called the Internet Protocol Processor (IPP). IPP offloads TCP and packet processing from the system to reduce CPU utilization, increase data throughput, and decrease network latency.
Multiprotocol Nishan IP storage switches support Fibre Channel switching, Gigabit Ethernet switching and wire-speed conversion between Fibre Channel and Gigabit Ethernet. The switches also support remote storage links across high-speed IP networks via iSCSI. Storage administrators can use them to connect existing Fibre Channel SANs through a standard interface or to build IP SAN fabrics that integrate Fibre Channel and iSCSI devices with data center, metro-area, or wide-area IP networks. Nishan calls its technology SoIP--Storage over IP. This is useful because even when users implement SANs, they cannot use their IP or Gigabit Ethernet WANs to link SANs, but instead must use expensive point-to-point dark fiber or optical multiplexers to connect FC SANs.
An Ethernet and IP-based storage fabric also lends itself to unified network management, with framework management applications reporting on networked DAS, SAN, and NAS installations. This approach allows for global IP traffic control, in-band or out-of-band management, traffic prioritization, bandwidth provisioning, authentication and VPN security, and improved policy-based management.
Nick Allen, Gartner vice president and research director, said, "iSCSI promises to let users operate SAN, NAS, LAN, and wide-area networks as a single, integrated network. This option will help IT managers choose storage, server, and networking technologies that are more easily managed, scalable, and cost effective. TCP/IP off load engines should go a long way toward leveling the differences in resource consumption among storage networking technologies."
Tim Bean, vice president of engineering at Finisar, sees a good deal of active iSCSI development in R&D labs at major storage and network developers. He doesn't believe that Fibre Channel will disappear from its niche markets and existing installations, but iSCSI will be vital for users who already have an Ethernet environment and who have not yet made the move to storage networking. "Fibre Channel is entrenched and has a niche in that space, but iSCSI opens it up to people who already have that architecture and structure in place. There's lot of energy in the market led by Cisco." He added, "You'll see more IP-based SANs which are purely IP-based when 10GB becomes more affordable." He thinks that will happen in the next twelve months. "There's an excitement in the R&D development world developing. There's significant investment in 10GB, and that's what's driving iSCSI development. Cost is coming down as new boards and chips are being developed."
Larry Boucher, founder of Alacritech and inventor of the SCSI protocol, said about iSCSI, "We're not trying to pick a fight with Fibre Channel, they're nice guys. But what is the real significance? If we look at the forest instead of the tree bark, does it really make sense to continue with two separate switching infrastructures?" He went on to say that the Fibre Channel industry is a year away from introducing comprehensive, heterogeneous 2GB SAN installations. Meanwhile, 10GB Ethernet is the enemy at the gate.
NAS/SAN storage networking is one of the fastest growing segments of the computer industry, with IDC forecasting growth from $9 billion in 2000 to $35 billion in 2004. Yet SAN installations have lagged far behind what storage vendors hoped, due to cost, lack of interoperability, and management complexity. And many companies are growing increasingly frustrated with what they see as a glaring dichotomy between the promises of new technologies such as iSCSI and the complex reality of today's storage networking. But with this new iSCSI development, IP-based storage networking may bring deliver on its promise. As Boucher pointed out, "The thing that's wonderful is all of this is the mainstream."
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|Publication:||Computer Technology Review|
|Date:||Feb 1, 2002|
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