IPS Devices—True Storage Gateways - Technology Information

Computer Technology Review, Sept, 2000 by Simon K. Fok, Jon W. Toigo

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.