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Scaling Blackboard for Large Scale Distance Learning
Communities
Steve Feldman, sfeldman@blackboard.com
online learning * Learning that takes place partially or entirely over the Internet.
The Online Momentum Shift • 66% of degree-granting post-secondary institutions in
the US offer online, hybrid/blended online and other distance education courses.1
• Over 4.6 million students were taking at least one online course during the fall 2008 term; a 17 percent increase over the number reported the previous year.2
• The 17 percent growth rate for online enrollments far exceeds the 1.2 percent growth of the overall higher education student population.
• By 2020, 50% of high school students will take an online course.1
3
Communities are Getting Larger
• State and County Initiatives
• Consortium Programs and strategic alliances between institutions.
• Content distribution networks
• New sources or revenue to reach markets and students that were not historically accessible – Non-traditional students are
being marketed to
Stakes are Getting Higher • Competition for funding by government
• Competition for revenue by students
• Learning modality changing with each technological innovation
• User expectations and online behavior changing constantly
• Hours of availability fighting toward mission critical – Often VLEs identified as 24x7 mission
critical systems, but resources to support are more like 8 x 5
Connected Learning Modality
Large Ac3ve Communi3es
Heavy Adop3on of Advanced Tools
Extended/Frequent Time in System
Richer Content and
User Experience
What are we modeling… Hundreds to Thousands Concurrent Sessions
Emphasis on Asynchronous & Synchronous Collaboration
Longer ClickStreams & Disposable Access
Larger pages, graphics/video, client-side interactions
Performance
Availability
Scalability
scalability* The ability for a distributed system to expand by accommodating greater levels of load while maintaining similar levels of performance.
Scalable Deployments • Emphasis on adoption of virtualization technologies
– Virtualization technology transparent to guest OS and application.
– Why: Take advantage of CPU and Memory expansion • Emphasis on fast provisioning
– Provisioning technology such as Dell AIM, VMWare deployment technology and XenServer deployment technology
– Why: Solved problems to minimize human error and fast deployment.
• Emphasis on diskless systems – Hardware is just “rented” space for CPU, Memory and
Network. – Why: Speed of network and storage so fast, why be
dependent on “wired” solutions.
performance* The amount of useful work accomplished by a computer system compared to the time and resource used.
Alternative Definition: Response time plus latency.
Responsive Deployments • Large 64-bid address space…
– It’s cheaper today than 4 years ago – Technology is heading this direction – It’s not a bad thing…
• Plentiful CPU worker threads… – Use only which you need – Take advantage of hyperthreading and MT technology – Partition via virtualization
• Many bigger…distributed environments
• Continuous maintenance – If you want to make your systems remain fast, you have to
“service” the roads. Lots of litter and potholes out there.
What is Performance? • Performance is quantifiable and measureable
• Performance is also perception
• Mostly recognized from a cognitive perspective – Instantaneous – Immediate – Continuous – Captive
Response Time Latency Performance
Realistic Approaches to Achieve Performance • Eliminate interface and resource contention.
– Better to have more capacity than queuing • Know your user behavior.
• Optimize for the saturated and low-bandwidth network conditions. – Enable Compression – Optimize Images – Cache Static Content
• Large JVM memory allocations are not a bad thing, but rather something to expect with Java-based applications. – Large JVM (4GB to 16GB) with aggressive options you understand.
• Two keys to the database – Continuous maintenance – Understand the key queries and how the CBO handles
availability* The capability to service a functional request without issue under conditions of desired performance and workload scalability.
What is Availability? • High-availability offerings mask the effects of a
system failure in order to minimize the impact of access and functional use of a system to a community of users.
• Simple Definition: – Percentage of time the system is in its operational state.
• You will often hear the concept of 3x9’s, 4x9’s or even 5x9’s – Planned versus Unplanned
• Availability = (Total Units of Time – Downtime) / Total Units of Time – 8760 hours in a year – Downtime = 10 hours – Availability = (8760 – 10)/8760 = 99.88%
Quick View into Availability Statistics Availability Percentage Model Unexpected Down8me per Year
90% 36.5 days
95% 18.25 days
98% 7.30 days
99% 3.65 days
99.5% 1.83 days
99.8% 17.52 hours
99.9% 8.76 hours
99.95% 4.38 hours
99.99% 52.6 minutes
99.999% 5.26 minutes
99.9999% 31.5s
Realistic Views of Availability • If the application is not functioning as expected, but you
can login, is it available? – Perception versus Reality – If it’s slow, do my users feel just as bad as if they received an
error? • How do you plan for unexpected?
– Practice really does make perfect • Do I treat the calendar from a date and time perspective
differently from an availability perspective? – Will my users cause problems if I take the site down during low
usage periods/dates? – Will the users even know that something happened? – Can I recover fast enough?
Realistic Approaches to Achieve Availability • Strategically picking redundancy in the architecture.
– Servers and storage make sense to a degree – Monitoring makes sense – Do advanced clustering architectures really make a difference? – Do the costs of a dedicated DR facility and site make sense?
• Choosing the right initiatives based on the resources available to manage – Don’t set your administrators up to fail. – If you don’t have the capabilities on-site, don’t be skeptical of
outsourcing the problem. • Balance costs over goals
– Choose the right places to put your pennies. – Make the business drive the decision…it’s their money!
Deployment: Availability
• VLEs are different beasts today then in the past. – Communities are bigger – Sessions last longer – Content is richer – Key point: Adoption is greater and users expect their sites up 24 x
7 x 365 • Architecture is designed for many parallel instances of the
product scaled in a horizontal fashion. – Distributed physical deployments – Virtualization is a key element
• Database failover more important than horizontal database scalability. – Emphasis on vertical database scalability
Deployment: Advanced Monitoring
• Measurement is the secret sauce for successful deployments. – Most reliable and scalable deployments measure beyond
the server infrastructure • Different types of measurements
– System/Environmental measurements – Business measurements – Synthetic measurements
• Collecting is only part of the prize – Need to analyze the data to drive business decisions from
the data.
Lifecycle of Measurement
Define Metrics: Goal SeVng
Iden3fy Method of Gathering: Isolate Tools and Processes
Implement Instrumenta3on: Begin Measuring
Align to KPI/ROI: Share with Stakeholders
Recommend Changes: Show Business Value
Reset Expecta3ons: New Ini3a3ves
Different Types of Monitoring
Synthe3c Monitoring
Real User Monitoring
Performance Forensic Monitoring
What is Synthetic Monitoring?
• Automated monitoring technique to measure the functional behavior of a system, sub-system or component.
• Typically a scheduled activity used to measure the availability, responsiveness and functional attributes of a common application scenario.
• Can be executed from any access point to the system in question, both internal or external.
• Also considered “Active” Monitoring of a system
• Not intended to supply load, but rather perform sampling of performance and availability
• Two methods: – HTTP Simulation or Real Browser Emulation
Tools for Synthetic Transactions • You can really use any form of HTTP emulation tool
like JMeter, Grinder, MSTS, LoadRunner, SilkPerformer, SOASTA, etc…
• Some monitoring software systems like Foglight, SiteScope, Nagios, CA IntroScope, Argent Defender
• External services: Keynote, Gomez (Compuware), WebMetrics, AlertSite, Pingdom, SiteUpTime
• Browser based solution: Selenium
Strategies for Synthetic Transactions • Site and Host Ping Tests should run on a multi-
second basis (15s to 30s)
• Common, yet critical paths targeting functional systems for availability should run on a continuous interval (x < 5 minutes).
• Complicated paths focusing on performance and availability should run every 30 to 60 minutes.
• Repeated tests when desired SLA or outcome not achieved
What is Real User Experience Monitoring?
• Passive web monitoring that observes web traffic to measure the user experience.
• Provides both quality of service and responsiveness metrics in order to gauge service levels of performance and availability.
• Typically a continuous activity watching silently in a parallel channel or as a pass through channel.
• Able to capture characteristics about the entire HTTP stream to be used for forensics and user incidents.
• Most vendors package as an appliance, but beginning to see the rise of “virtual” appliances.
• Synthetic monitoring is just not enough…
Tools for RUM Monitoring • Dominated by commercial vendors who have a niche in
web performance and/or application performance management. – Quest FxM – Coradiant TrueSight – Oracle Real User Experience Insight – Tealeaf – CA/NetQoS
• Rise in new tools coming from network equipment vendors like Cisco, Opnet and Citrix/NetScaler
Strategies for RUM Monitoring • Identify areas of dense usage in order to highlight
performance, availability and functional experience in most common components of system.
• Start with a wide lens of traffic watching and slowly narrow the area of focus to minimize the “purge” of data.
• The “purge” of data is going to happen, so be prepared to move the data out of the system into an alternative repository. – Some of the vendors have already solved this problem via an
Enterprise Data Warehouse (eg: Coradiant BI) • Most of these tools can show
– Time 2 First Byte, Host Latency, Network Latency and E2E • Avoid the trap of focusing on Time 2 First Byte
– You are serving an entire application from client to server
What is Performance Forensic Monitoring? • Deliberate instrumentation approach to capture
performance characteristics about an application deployment.
• Measures resource and interface statistics not typically visible from the application directly.
• Provides data points about application code execution that can be tied down to both the user and/or the application component.
• Can’t measure everything, but can sample consistently. – Certain data points can be captured on a continuous basis such
as Java/J2EE container statistics
Tools for Forensic Monitoring • Recommended tool sets tie the PFM tool with the RUM
tool. – Foglight FxM seemless integration with Foglight Application
Cartridges and Database Performance Analysis – Coradiant TrueSight integration with Dynatrace APM (Coradiant
AV) – CA NetQoS integration with CA Wily IntroScope – Oracle RUE Insight with Oracle Enterprise Manager for
Applications and Databases. • Limited supply of open source tools that can perform a
fraction of the functionality. – No known integrations with RUM tools – Point based tools per container (not aggregators) – Example tools: JConsole, Java VisualVM
Strategies for Forensic Monitoring • Measure the essentials such as container interfaces and
resources.
• Most vendors have rule agents to begin sampling with a greater degree of instrumentation when certain rules are broken.
• Retain statistics for extended periods of time (greater than 1 year) for annual, month, weekly, daily and hourly comparison purposes.
• Construct trending thresholds for alert purposes to invoke a planning exercise in advance of an incident. – Yes application forensics can be used for trending purposes for
events in the future as they are based on events in the past as points of reference.
Please provide feedback for this session by emailing BbWorldFeedback@blackboard.com.
The subject of the email should be title of this session:
Scaling Blackboard for Large Scale Distance Learning Communities
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