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Thinklogical White Paper: Redundant Fiber-Based Systems
 

Thinklogical White Paper: Redundant Fiber-Based Systems

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This white paper illustrates the concept of redundant and resilient systems and how fiber-based extension and routing solutions can maintain operability in the event of a failure.

This white paper illustrates the concept of redundant and resilient systems and how fiber-based extension and routing solutions can maintain operability in the event of a failure.

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    Thinklogical White Paper: Redundant Fiber-Based Systems Thinklogical White Paper: Redundant Fiber-Based Systems Document Transcript

    • WHITERedundant Fiber-BasedSystems A Thinklogical White Paper By Larry Wachter Senior Product Manager - Routing and Extension Solutions - Thinklogical This white paper illustrates the concept of redundant and resilient systems and how ber-based extension and routing solutions can maintain operability in the event of a failure.   www.thinklogical.com
    • White Paper - Redundant Fiber-Based SystemsIntroductionAt the most basic level, availability can be de ned as the probability that a system is operatingsuccessfully when needed. The term high availability has been used to encompass all things related toproductivity, including reliability and maintainability. The adoption of high availability has led toredundant and resilient systems spurring a ripple e ect and ending with the creation of berinfrastructures which require products and solutions that provide various levels of fault-tolerance. Inparticular, this is true of ber-based routing and extension solutions, which not only provide mechanismsthat aid in modular redundant system architecture, but also provide high bandwidth, cost-e ectiveness,and support for complex topologies. Consequently, Thinklogical has designed a redundant ber-basedrouting and extension solution that meets the requirements for reliable signal transmission in modularredundant system deployments.High Availability Achieved Through Redundant and Resilient SystemsRedundancy can involve a variety of technologies, all of which pertain to physical backups, whereasresiliency deals primarily with communication protocols. A redundant device may activate as a result of afailure, but without built in resiliency as well, there could be data loss, or worse, the inability to establishthe redundant connection. A resilient system will return to an operable state after encountering trouble.Therefore, if a risk event knocks a system o ine, a highly resilient system will resume its intended workand function with minimal downtime.Building a redundant and resilient system requires a holistic mentality. One must prioritize everyforeseeable risk and then determine not only how to reduce the risk in the rst place, but determine howto minimize its impact on the system. The need or requirement for redundancy can be based on a set ofsystem criteria questions: Does the system need to run around the clock and is downtime unacceptable? If a system fault occurs, should the primary system switch over to the secondary system seamlessly? What is the degree to which the data shared between sources and destinations must remain constant and reliable? How can single points of failure within the system be minimized and how can one ensure that components within the infrastructure will not stop the overall operation of the system?2 www.thinklogical.com
    • Application Diagram BROADCAST & POST-PRODUCTION BRIEF White Paper - Redundant Fiber-Based Systems High availability, achieved through redundancy and fault tolerance, is a critical component of many routing and extension installations, especially in secure visual computing environments. While the loss of an enterprise system for a few minutes is inconvenient, losing a secure visual computing system can have disastrous consequences. Some form of redundancy and fault tolerance is generally used if a control system shutdown or loss of visibility causes a major loss of revenue, loss of equipment, disruption to public services and/or safety. Redundancy in these situations means the duplication, or even triplication, of equipment that is needed to operate without disruption, if and when the primary equipment fails during the mission. In these types of environments the cost of failure is so high that a redundant system approach is crucial. By using a ber-based solution that supports redundant system design, users enjoy highly reliable data transmission, reduced costs of deployment and a guaranteed upgrade strategy as requirements evolve. This white paper will touch upon several various redundant and fault tolerant features and architectures for ber-based infrastructures, but will focus primarily on Dual Modular Redundancy, otherwise known as Parallel Redundancy, which is the approach taken by Thinklogical systems. This paper will also highlight features within the Thinklogical product lines that can help achieve higher availability. Redundancy on a Component Level The most important place to start to guarantee reliable operation is to provide redundant, hot-swappable components. It is also critical that modules or components should be capable of being removed, replaced or added to the system without interruption. Replacements should not need rewiring or reprogramming. In addition, many innovations have been created, such as state-based control and self-learning diagnostic routines, which have raised the ability of the controller to detect, annunciate and describe problems within the components. For many users, the ability to maintain and revise the system without shutting down o ers an acceptable level of availability, especially if the change or repair can be completed in minutes. 3 www.thinklogical.com
    • White Paper - Redundant Fiber-Based SystemsCritical system components: Uninterrupted power supply (UPS) Redundant power supplies Redundant components - Chassis - Processors - I/O modules - Sensors and actuators - PCs/HMI - Networks - Media - Servers - DatabasesThinklogical’s System ContingenciesPower supply redundancy is a very popular means to increase system reliability. A single power supplyfailure could have a catastrophic e ect that equates to a tremendous amount of lost revenue. This needfor system integrity and guaranteed performance in these demanding conditions necessitates powerredundancy. Therefore, all of Thinklogical’s routing and modular extension products are equipped withredundant, hot-swappable power supplies.Thinklogical’s VX and HDX line of routers are designed with hot-swappable critical system components,such as cooling fans and pluggable optics (SFP+), thus minimizing business impact in the unlikely eventa component should fail. The hot-swappable I/O boards also provide excellent in-service expansioncapabilities allowing the router to be recon gured without interrupting signal processing by poweringdown the router. In addition, the HDX Router line is equipped with dual controller cards with the abilityto switch between cards in the event of a failure.4 www.thinklogical.com
    • White Paper - Redundant Fiber-Based SystemsModels of RedundancyThere are a number of common redundancy models used in the industry, such as Standby Redundancyand Dual Modular Redundancy, or Parallel Redundancy.Standby RedundancyStandby Redundancy refers to a con guration where there is an identical secondary unit to backup theprimary unit. Under standby redundancy they do not share any of the load and they start operating onlywhen active components fail. In addition, a third party may be needed to monitor the system and givethe command when a switchover condition is met.In standby redundancy, the components are set to have three state: Cold, Warm and Hot Standby.Typically in Cold Standby the secondary unit is powered o in order to preserve the life of the unit. Thedisadvantage of this model is that there is a signi cant time delay in getting the replacement system upand running. While the hardware and software are available the unit needs to be powered up before itcan be brought online into a known state.Warm Standby has a faster response time because the backup (redundant) system is always running andregularly synchronized with the Device Under Control (DUC). When a failure occurs on the primarysystem, the redundant system can disconnect from the failed system and connect to the backup system.This allows the system to recover fairly quickly (usually within seconds) and continue to work. Althoughsome data will be lost during this disconnect/reconnect cycle, warm standby can be an acceptablesolution where some data loss can be tolerated.In these types of redundant models the switching is not seamless and adds to the probability of failurewithin a given system. To o set this increased probability, additional hardware (a third party voter) canbe added to the redundancy con guration to help assist in the switching from the primary to secondarysource. While these system components add to the reliability, they are normally connected in series,which creates a hybrid parallel-series connection and introduces another point of failure for the system.In addition, the system cost typically doubles with the additional hardware.5 www.thinklogical.com
    • White Paper - Redundant Fiber-Based SystemsHot standby means that both the primary and secondary data systems run simultaneously and both areproviding identical data streams to the downstream client. If the primary system fails, the switchover tothe secondary system is intended to be completely seamless, or “bumpless,” with no data loss. HotStandby is the best choice for systems that cannot tolerate the data loss of a Cold or Warm Standbysystem. There are some variations of the Hot Standby model, such as Dual Modular Redundancy orParallel Redundancy. The di erentiating factor between these models is how tightly the primary andsecondary units are synchronized.Dual Modular Redundancy (DMR) or Parallel RedundancyThe approach of having multiple units running completely synchronized and in parallel is known asDMR, or Parallel Redundancy. This model typically has rapid switchover time.There are three basic tenets of dual system redundancy:1. Physical separation of signal paths2. Dual-chassis redundant signal controllers3. Synchronization of status informationA DMR routing and extension system is con gured with two tightly synchronized primary andsecondary routers running in parallel. These routers mirror one another with identical signals beingsent through both of them at the same time. These signals are sent to their destination at a receivercomponent. Deciding which unit is correct can be challenging if you have more than one router.Having to choose which unit you are going to “trust the most” defeats the purpose (by arbitrarily givingone router priority without dynamic review of operating parameters). Also monitoring and determiningwhen to switch to the secondary unit can be complicated.6 www.thinklogical.com
    • White Paper - Redundant Fiber-Based SystemsThe Thinklogical AdvantageThinklogical has designed a cost-e ective, resilient solution to take the complexity out of the DMR approach.The feature is designed into the SDI Xtreme 3G+ Receivers, and is known as a “switchover capability.” This allowsthe component to receive identical streams on both input bers. By default it will attempt to synchronize to the‘primary’ ber by searching for the synchronization characters in the received stream. Simultaneously, it will alsocheck the ‘secondary’ ber and attempt to synchronize to its stream. After a pre-determined amount of time,whichever stream the receiver locks on to will be selected and the SDI data will then be decoded from thatstream. In the event that the selected stream loses synchronization, the receiver will automatically switch to theother stream. There will be minimal loss of SDI video during this switchover. In order to prevent switching backand forth between an intermittent signal, the receiver will continue to use the ‘switched-over’ stream regardlessof whether or not it re-acquires lock to the original stream. If an event occurs such that the switched-overstream loses lock, then the receiver will attempt to switch back over to the original stream.7 www.thinklogical.com
    • White Paper - Redundant Fiber-Based SystemsThis synchronization scheme ensures the maximum uptime in the event of a failure at any point in thesystem. Interestingly, this approach mirrors the classic design common among disaster recoveryimplementations. In fact, most highly available systems stick to this simple design pattern: a single,high quality, multi-purpose physical system with comprehensive internal resiliency runninginterdependent functions paired with a second, physically separated, duplicate system. The overridingpurpose of this design is the prevention of, or rapid recovery from, a failure, which allows a system tocontinue to operate despite a partial or complete failure of any signi cant component.SummaryThe idea of redundancy is not di cult to grasp, but implementing it takes some thought. An initialdecision on Cold, Warm or Hot Standby will impact all aspects of the implementation. The choice ofproper hardware and robust system architecture is critical for a well functioning system.It is clear that organizations cannot fully leverage the bene ts of redundancy models without acomprehensive routing and extension solution. Thinklogical’s system solutions o er innovativeorganizations the ability to create high density, scalable and redundant system architectures thatdeliver broad functionality and provide high ROI. It is very important to keep in mind that lowersystem cost doesn’t always equal lower total cost of ownership. More importantly, the cost of oneunplanned shutdown far outweighs the costs of redundancy. If data connectivity is crucial to thesuccess of the company or organization, it would be wise to consider the possibility of installing aredundant system and to weigh the options carefully when choosing the key components.About ThinklogicalThinklogical is the leading manufacturer and provider of ber optic KVM/video extension solutions,and ber matrix routers and switches. Organizations worldwide rely on Thinklogicals products andsolutions for optimal performance in secure visual computing environments. Through pioneering nextgeneration ber optic extension, switching, and server management technologies Thinklogical helpscustomers reduce cost and simplify the management of complex computing infrastructures. © 2011 Thinklogical. All rights reserved. Thinklogical claims or other product information ¡ contained in this document are subject to changeExtend Distribute Innovate without notice. This document may not be reproduced, in whole or in part, without the express written consent of Thinklogical.September 2011