Storage over SONET for business continuance

Posted on July 01, 2003

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Here are the arguments in favor of using SONET for applications such as business continuity and extending storage over WANs.

By Elaine Bird

In today's 24x7 business environment, enterprises' dependence on advanced eBusiness solutions is intensifying and triggering unprecedented growth of mission-critical data. Recent technology advancements have caused an explosion in the amount of information being stored by companies across the globe, and protecting critical data is one of an IT organization's most important responsibilities. In an era of heightened risk, it is imperative that enterprises protect these burgeoning volumes of data and the applications that generate them.

Business continuity planning has never been more essential to an enterprise's survival. Whether protecting against a natural or man-made disaster or even a technology failure, standard storage networks that transport mission-critical data over short distances do not afford sufficient protection. Enterprises must ensure that business critical information is protected, replicated, and stored in geographically disparate data centers.

Juxtaposed with this are the budget constraints and limited IT and personnel resources that many enterprises currently face, as well as the need to reduce storage total cost of ownership. While an enterprise's need to extend storage over distance is critical, equally critical is the need to realistically assess the options for meeting those needs in the context of available resources. To address both their business continuity and economic criteria, enterprises seek an economical and reliable storage platform that fosters high performance, availability, flexibility, and security over WAN distances. This storage-over-distance solution must enhance operational efficiency by optimizing IT productivity and investment in existing IT resources, as well as streamline storage networking operations. Enterprises need to do more with fewer resources to address explosive storage growth.

Storage WANs enable enterprises to dramatically extend their storage capacity and back up business-critical information and applications to geographically dispersed data centers by carrying business continuance applications across existing metro and national network infrastructures. To experience the same high throughput, low latency, zero data loss, and security levels that companies have come to expect from their on-site storage networks—while containing costs—enterprises must carefully assess their technology options.

Meeting business continuance objectives

To efficiently and cost-effectively build or extend a storage WAN to meet current and future business continuance needs, enterprises should try to

Leverage existing infrastructure—Whether a company has already built a storage infrastructure and deployed capital-intensive networking, such as dense wavelength-division multiplexing (DWDM) and channel extenders, or is extending its business continuance applications for the first time, it should leverage existing infrastructure to contain costs. In addition, the enterprise's various data-center protocols—Gigabit Ethernet, Fibre Channel, ESCON, and FICON—as well as NAS, SAN, LAN, and mainframe applications, were not developed with the notion that they would be stretched over extended distances. So, the infrastructure must provide native support for all existing storage protocols to make the most of existing resources, without incurring substantial additional costs. This is possible with storage extension solutions.

Increase bandwidth utilization—Traffic and congestion can slow and even interrupt applications using data storage networks. A WAN must be able to dedicate bandwidth to efficiently transport data from a variety of protocols—such as Fibre Channel, Gigabit Ethernet, FICON, and ESCON—while leaving the remaining bandwidth for other links.


SONET is one option for transporting data over MAN/WAN distances for applications such as business continuity and disaster recovery.
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Reduce network complexity—Storage over DWDM WANs may start out simple when the first channels are installed, but as the system grows, inline amplification and optical power control mechanisms need to be installed and operated to support higher channel counts. Storage over other types of WANs may require multiple pieces of equipment to successfully transport data-center protocols. These issues increase complexity, difficulties with fault isolation, and equipment and operational costs. As a result, enterprises should try to enhance performance without increasing complexity.

Monitoring and visibility—Maintaining visibility and monitoring the performance of the network is also key for reliable storage WANs because it enables rapid detection and isolation of errors.

Optimize quality of service (QoS)—All of these capabilities are essential to ensuring the highest QoS for a storage WAN and the accompanying storage networking applications, such as tape/disk backup, synchronous/asynchronous disk mirroring, and server geo-clustering between geographically dispersed data centers. By maximizing network bandwidth and flexibly directing traffic streams, enterprises can achieve significant first-time cost savings and create a simpler operational model, while lowering maintenance costs, optimizing network throughput, and reducing latency.

Maximize personnel resources—During these tight economic times, many enterprises have had to reduce and spread IT personnel resources. So, when extending a storage WAN environment, companies should consider technology that increases performance and improves monitoring without requiring additional resources or expertise to manage the WAN.

'SONETizing' storage over WANs

In theory, WANs provide an efficient, reliable, and safe network for companies that want to connect and store business-critical information in geographically dispersed locations. However, in practice, enterprises typically do not have a network designed to support various data-center protocols, multiple applications, and several platforms that might include SANs, NAS, and LANs.

In addition, until recently, it has been cost-prohibitive for companies outside the Fortune 50 to access the MAN/WAN for business continuance using their own private networks.

In general, enterprises choose their LAN and SAN networking technology from the following types of existing MAN/WAN infrastructures: IP/Ethernet, DWDM, dark fiber, and/or SONET.

Some of these technologies have characteristics that limit their application for storage over WANs.

IP is ubiquitous but often cannot satisfy the QoS requirements of business continuance applications and can cause network congestion resulting in retransmission of data. In addition, IP may not be sufficiently secure or reliable to protect business-critical data.

Dark fiber is expensive and hard to access. Issues with DWDM systems, besides high prices, include fiber distance restrictions, poor bandwidth utilization, and high operating expenses associated with network troubleshooting

Synchronous Optical Network (SONET) or its international equivalent, Synchronous Digital Hierarchy (SDH), is a ubiquitous, scalable, and economical network transmission technology available from virtually any carrier, with a variety of digital line and trunk capacities.

In fact, analysts estimate that more than 150,000 SONET rings are deployed in North America, interconnecting every major urban center. This means that most businesses in North America can immediately access SONET today.

A "storage-over-SONET" device enables enterprises to leverage existing network connections and SONET's performance optimization capabilities to transport data without adding extra layers to the network. A storage-over-SONET extension device puts assorted protocols into a SONET payload and enables information to be transported over long distances without limitations. The use of SONET payloads ensures that each storage application has its own secure, deterministic data path throughout the network.

This technology also enables enterprises to monitor, report, and provision network traffic to minimize performance issues and facilitate rapid fault isolation, and provides a physical layer of isolation for data security.

As a result, enterprises can now achieve over "five 9s" data availability and high network and storage management performance.

In addition, SONET ensures that ser-vice level agreements (SLAs) specific to enterprise storage networking requirements can be defined and enforced, so an enterprise can go back to the carrier with evidence that they did not meet their SLA, with data on parameters for data throughput, network latency, and SAN equipment health monitoring.

Using SONET technology, companies can multiplex mixed storage protocols through the enterprise's existing network, whether it be SONET/SDH, DWDM, or dark fiber, while connecting through one of many WAN interface options (DS-3, OC-3, OC-12, or OC-48), providing integrated data compression on all protocols and transporting both storage and non-storage traffic on a single network connection.

Data compression significantly reduces the size of the data loads to be transported over the network and enables enterprises to use bandwidth more effectively by placing multiple applications on one connection. When combined with the ability to dynamically share MAN/WAN bandwidth between multiple technologies with low latency, data compression allows for up to 10 times more efficient use of WAN bandwidth and can reduce operational costs. Also, software-tunable port capabilities allow an enterprise to configure ports from Fibre Channel to FICON, ESCON to FICON, or any other combination.

SONET technologies also offer visibility and control from a single point when transmitting data from multiple applications and platforms between data centers. SONET can improve performance monitoring of a network to rapidly detect and isolate errors. These capabilities enable enterprises to minimize MAN/WAN networking costs, make WAN choices that align with their requirements, and obtain the performance required to meet their application networking needs regardless of whether they are leveraging SONET, DWDM, or dark fiber.

Business continuance and consolidation have never been more important to today's enterprises. Business environments are volatile, unpredictable, and under intense competitive pressure. And with constrained IT budgets, enterprises have to do more with less to reduce IT costs with an adaptive infrastructure for storage. SONET enables enterprises to meet their storage extension needs through assets they already own or lease, ensuring that business-critical data and applications are transmitted efficiently and securely between geographically dispersed data centers.

SONET creates a simpler operational model to transport a variety of traffic types (e.g., NAS, SAN, LAN, mainframe) over a single network connection. In addition, by optimizing network bandwidth and flexibly supporting multiple concurrent applications and protocols, enterprises can dramatically improve network throughput, reduce latency, and maintain QoS. Most importantly, storage over SONET enables enterprises to ensure network and data storage, security, reliability, and availability while lowering maintenance costs and saving capital costs.

Elaine Bird is director of marketing at Akara Corp. (www.akara.com) in Ottawa, ON, Canada.


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