Optical Networks for The Enterprise: The Broader View - Storage Area Networks, Network Attached Storage - Technology Information

Computer Technology Review, June, 2001 by Jerry Zeisler

Storage Area Networks (SANs) and Network Attached Storage (NAS) are the buzzwords in today's Enterprise and Service Provider space. Their popularity is due to the increased demand not only for access to the storage facility itself, but also for the flexibility they provide in controlling information.

In the midst of all of this hoopla about storage and SANs and NAS are the basic business requirements for moving, storing, accessing, and managing information--not only within a single data center, but between two or more data centers. Driving the movement toward integrating and leveraging multiple data centers are applications such as high availability, backup and recovery, data vaulting, and information sharing.

Making the Connection with Fiber Optics

To move information between sites efficiently and effectively within a metropolitan area, many businesses are taking a serious look at fiber optic connectivity. Until now, most storage vendors and solution providers have been taking the narrow view that the killer application for optical networks within the metropolitan area is storage access.

While it is true that remote storage access for a Disaster Recovery application can provide a reasonable justification for building a Storage Wide Area/Metro Area Network (SWAN or SMAN) using optical connectivity, this is a limited view. Looking at it more broadly, a fiber optic network connecting multiple sites allows a business to build a much more powerful business tool--a geographically dispersed Systems Area Network.

Optical Systems for the Enterprise

The optical multiplexing technology being used today for metropolitan area connectivity for the enterprise is Wave Division Multiplexing (WDM) or its more current adaptation, Dense Wave Division Multiplexing (DWDM). This type of connectivity can provide a business with much more than simply access to massive amounts of storage at high speed across a region. DWDM optical networks offer tremendous capacity, scalability, availability, and protocol transparency that other technologies can't provide. The underlying value of a DWDM network is in understanding how to leverage those features effectively, and what the implications are to the business and the applications in using this technology.

Major Features of a DWDM Optical Network

A DWDM optical network offers a substantial number of features, including:

* Capacity, Bandwidth, and Speed, and lots of it--up to about 640Gbps (Gigabits per second) per system today. Protocols and applications can all run at their native speeds, i.e., 17MB (MB/sec) for ESCON, 1.062Gbps for Fibre Channel (FC)--2.12Gbps soon--and 1.25Gbps for Gigabit Ethernet (GbE). Relative to traditional carrier circuit technologies, a DWDM optical network today has a capacity 14,222 times that of a D53/T3 circuit (45Mbps), about 4,129 times that of an OC3 circuit (155Mbps) and 512 times that of a single Gigabit Ethernet or Fibre Channel connection (1.25Gbps or 1.062Gbps respectively).

* Scalability--some vendors can support up to nine sites in a protected optical ring--a highly available topology, and up to 160 channels. There's nothing to stop you from building multiple optical networks and tying them together with devices such as Fibre Channel, Ethernet, or ESCON switches or directors.

* Protocol Transparency/Low Latency--Most DWDM systems support Fibre Channel, ESCON, ATM, FICON, GbE, SONET/SDH, Sysplex Coupling Facility timers, and video. Little latency through the device is noticed because only modest processing is required to direct the optical signal from the input to the appropriate laser or vice versa.

* Availability--Different vendor architectures provide different levels of availability, but overall, redundancies are either built-in or can be implemented externally. There are costs and implications associated with each option.

* Long life span--DWDM optical connectivity in the Enterprise is in its infancy yet is proving to offer an effective competitive edge. Along with wireless, communication over fiber optics will be around for a long time to come.

Applications

With all these features available, it becomes fairly obvious that an extensive array of both old and new applications can now be deployed between multiple data centers across a region using a single, consolidated infrastructure that before was either ineffective, inefficient, or impossible to implement. This applies to both mainframe and open-systems applications.

* Disaster Recovery. Backup and recovery processes become much more effective providing a real opportunity to reduce downtime, thereby lowering risk and reducing losses. Imagine the decrease in recovery time using several 1Gbps Fibre Channel links to restore data to a primary disk subsystem from one that's remote, rather than across a single ATM connection at 155Mbps typically in use today. A single Fibre Channel link provides about a five-fold decrease in the time to recover versus a 155Mbps connection. And it's quite possible to have multiple Fibre Channel connections transferring data simultaneously.