IPS Devices--True Storage Gateways.

Enabling a broad range of connectivity options

With Internet Protocol Storage (IPS), storage devices can be made available to any software process on any server across virtually any popular network interconnect. The software architecture of the IPS device is entirely modular to support a broad range of device connectivity options, including:

* Target and Host Mode for SCSI.

* Target and Host Mode for Fibre Channel.

* Target and Host Mode for InfiniB and.

* IP stack processing for Gigabit Ethernet.

* IP stack processing for ATM/SONET.

In practical terms, this means that the IPS enables any-to-any connectivity between storage devices and servers. As shown in Fig 1, storage in a web server environment is separately connected to each web server and application server in the network. A backup server has also been configured on the network with an attached tape silo for performing backups of data across the network.

In the case illustrated in Fig 1, the company is experiencing difficulty in accomplishing backups with web and application servers online. Production network bandwidth is negatively impacted as long data transfers are made to the silo. Given the investment in tape silo hardware, the company sought a method for accomplishing a backup without sacrificing the silo.

Fig 2 depicts the solution, which involves the implementation of three IPS hardware devices and the reconfiguration of all storage resources along a broadband network interconnect. This interconnect could be SCSI, Fibre Channel, ATM/SONET, Gigabit Ethernet, or any of a number of other networks providing adequate bandwidth and performance characteristics for supporting storage I/O requirements. The backup problem is resolved with no change to legacy hardware. IPS devices not only enabled the sharing of storage resources more efficiently, but also enabled the removal of the server device associated with the tape silo.

In this highly simplified example, one can readily see the basic function of an IPS device. In some respects, it resembles certain "protocol router" products already available on the market for bridging legacy SCSI devices to Fibre Channel SANs. A major difference, however, between these products and the IPS is its specialized software, which enables the IPS device to deliver flexibility, functionality, modularity, and performance that ensures any-to-any connectivity between the storage device and server host. Not a simple bridge-router, the IPS is a true storage gateway.

As depicted in Fig 3, an IPS device serves as a true SAN router. In the Gigabit Ethernet SAN, the Gateway translates all server SCSI I/O transfers to Gigabit Ethernet and directs them to the Gigabit Ethernet switch. Presumably, a subnetwork can be established via the switch that is dedicated to I/O transfers only. Once data traverses the switch to this subnetwork, a second IPS device translates all data to native SCSI to work with the attached storage devices. Additional support can be provided to handle a mixture of storage device interfaces if the company employs a mixture of SCSI and Fibre Channel device types.

The bottom example in Fig3 shows how Fibre Channel Adapters on hosts may be connected to one of the current generation of Fibre Channel SAN switches without the need of protocol translation. On the storage side of the switch, an IPS device can be used readily to translate SCSI to Fibre Channel in order to utilize the SCSI storage devices.

One of the strengths of evolving SAN topologies is their flexible implementation across distances. Major Interexchange Carriers (IXCs) are presently working to deploy SONET/ATM Metropolitan Area Networks (MANs) directly to the corporate premise in major U.S. cities. The objective is to enable companies to consolidate voice and data traffic onto these highly secure, high performance (0C3/OC 12+) networks. Given the bandwidth available in these networks, cost-effective remote site mirroring and remote tape vaulting will become feasible for a growing number of companies. IPS devices can facilitate this strategy, as well.

The IPS device, when strategically deployed, enables the consolidation of traffic from SCSI storage arrays and a Fibre Channel SAN in the branch office and the translation of the combined data streams across a Gigabit Ethernet link to a router that connects to the high speed Metropolitan Area Network. At the destination, another IPS device enables the data stream to be translated from Gigabit Ethernet to Fibre Channel or SCSI to drive the tape silo.

IPS Devices solve Real-World Problems Today

IPS devices are not the only approach to the Storage Dilemma that is being explored in the industry today. Some vendors are working on NAS-like products that will afford access to back-end SANs through NAS-based "portals." Others are working to develop workarounds to server operating system file systems that will enable the true sharing of physical storage and stored data among heterogeneous hosts. Meanwhile, corporate IT professionals continue to confront practical issues of storage proliferation, access, and management.

IPS devices can be optimized for long block transfers, malting them ideal for large data movements such as replication and backup/restore. Short block transfers are being optimized in current testing and all transfer rates will be published once they have been tested, documented, and confirmed.

In summary, IPS devices should be considered a superior data storage option for the following reasons:

* They can be implemented immediately to offload storage-related data transfers from overburdened LANs. In backup/restore applications, placing data transfers on a dedicated high bandwidth link (whether across a SAN fabric or in a straightforward, point-to-point connection) can deliver a tenfold improvement in storage-and-retrieval operations.

* They operate transparently and require no changes to existing networks, systems, or storage devices.

* InBand Management in an ISP device enables autodiscovery of existing storage devices and interconnects and facilitates dynamic reconfiguration of the storage network as storage devices are placed into and taken out of service.

* They can provide an alternative to server-tethered storage device configurations in some cases, minimizing the acquisition costs and maintenance expense for unnecessary servers.

* They can be deployed in many more settings than conventional SCSI-Fibre Channel bridges and offer flexibility to support evolving storage topologies. Analysts claim that, regardless of the continuing development of SAN technology, the next decade will see the perpetuation of numerous storage topologies within companies, including homogeneous and proprietary SANs, standalone and server-tethered disk arrays, legacy SCSI and newer Fibre Channel disk and tape devices, and Network Attached Storage devices. Only an IPS device can provide the any-to any connectivity that will be required to bring all of these diverse storage topologies together, so they can be managed centrally.

Storage Area Networks promise to solve many storage-related problems, including issues of performance, data sharing, management, scalability, and resilience. However, considerable work remains to be accomplished before open SANs move out of the "visioneering" stage and become workable solutions for the modern, heterogeneous, corporate IT environment.

In the interim, companies require immediate solutions to the storage networking issues that they are confronting today. IPS devices provide a robust solutions set for interconnecting storage resources and servers.

Simon K. Fok, Ph.D. is the president and chief executive officer at NetConvergence, Inc. (Santa Clara, CA) and Jon W. Toigo is the president at Toigo Productions (Dunedin, FL).