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High-Availability for XenAppWith XenServer and NetScalerFebruary 4, 2009
Daniel Feller, Sr. Architect Worldwide Consulting Solution
2© 2008 Citrix Systems, Inc. — All rights reserved
Agenda
Overview
Layered High-Availability
Hardware Layer
Component Layer
Intra-Site Layer
Inter-Site Layer
Next Steps
3© 2008 Citrix Systems, Inc. — All rights reserved
Disaster Recover: Major Outages
T ra n s it S tr ik e
E a r th q u a k e
S n o w s to rm
T y p h o o n
T s u n a m i
B o m b in g
P a n d e m ic
4© 2008 Citrix Systems, Inc. — All rights reserved
Disaster Recovery
Layered High-Availability
6© 2008 Citrix Systems, Inc. — All rights reserved
High-Availability Layers
• Hardware
• Components• XML Broker• Web Interface• Mission critical XenApp Servers
• Intra-Site
• Inter-Site
7© 2008 Citrix Systems, Inc. — All rights reserved
Initial Architecture
Access Gateway172.16.0.22
Access Gateway172.16.0.27
User
User Web Interface172.16.0.51
Web Interface172.16.0.52
XML Broker172.16.0.53
XML Broker172.16.0.54
Web Interface172.16.0.58
XML Broker172.16.0.59
Site Minneapolis
Site Ft. Lauderdale
Hardware Layer
9© 2008 Citrix Systems, Inc. — All rights reserved
Hardware Layer
• Hard stop of server
• Complete disruption in service
• Solution:
Critical Failure
• Degradation of hardware components
• No disruption in service for time being
• Solution:
Imminent Failure
Overview
10© 2008 Citrix Systems, Inc. — All rights reserved
Shared Storage
Hardware LayerXenMotion
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• Configuration• Enter Maintenance Mode• Accept XenMotion• XenMotion• Repair server• Exit Maintenance Mode• XenMotion
• Failover• Virtual servers move without user impact• Able to mange immanent failures before
they become critical
Hardware LayerXenMotion Configuration
12© 2008 Citrix Systems, Inc. — All rights reserved
High Availability
Shared Storage
13© 2008 Citrix Systems, Inc. — All rights reserved
Hardware Layer
• Configuration• Enable HA• Select heartbeat storage• Define protection levels
• Calculates number of XenServers that can fail• Adjusts based on size/resources
• Implement
• Failover• Protected servers have highest priority• Pool restarts virtual machines until
resources exhausted
XenServer High-Availability
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Hardware LayerBest Practices
XenApp Role Protection Level Justification
Data StoreLicense Server
Protected Only one of each. Critical to proper functioning of Farm
Data Collector Primary: ProtectedSecondary: Do Not Restart
Primary: XenApp only uses oneSecondary: Resources better used for other XenApp roles
Application Hub
Primary: ProtectedRedundant: Do Not Restart
Must have one to stream applications. Redundant hub’s resources better used for other XenApp roles
Web Interface Primary: ProtectedRedundant: Do Not Restart
Must have one to enumerate/launch applications. Redundant Web Interface resources better used for other XenApp roles
XenApp SiloMission Critical
Protected These servers deliver the most important applications in the farm. Guaranteed availability is a must
XenApp SiloOther Apps
Partial: ProtectedPartial: Restart if Possible
Have enough servers protected to deliver to a percentage of the user population, while not impacting availability of mission critical services.
Component LayerHigh-Availability
16© 2008 Citrix Systems, Inc. — All rights reserved
Component Layer
• Manages application authentication, enumeration and launch requests
• Potential black hole
• Solution:
XML Broker
• Single point of access for applications
• Potential black hole
• Solution:
Web Interface
Overview
17© 2008 Citrix Systems, Inc. — All rights reserved
Component Layer
• Web Interface Monitor• Validates Web Interface server, service and site responds correctly• Overcomes Web Interface Black Hole• Interrogates the Web Interface Site Path
(www.company.com/Citrix/AccessPlatform/site/default.aspx)
• XML Broker Monitor• Validates XML Broker services responds correctly• Overcomes XML Black Hole• Queries XML Broker for published application load
NetScaler Smart Monitors
18© 2008 Citrix Systems, Inc. — All rights reserved
Component Layer
• Web Interface Monitor• Validates Web Interface server, service and site responds correctly• Overcomes Web Interface Black Hole• Interrogates the Web Interface Site Path
(www.company.com/Citrix/AccessPlatform/site/default.aspx)
• XML Broker Monitor• Validates XML Broker services responds correctly• Overcomes XML Black Hole• Queries XML Broker for published application load
NetScaler Smart Monitors
19© 2008 Citrix Systems, Inc. — All rights reserved
Component LayerArchitecture
Access Gateway172.16.0.22
Web Interface172.16.0.51
Web Interface172.16.0.52
XML Broker172.16.0.53
XML Broker172.16.0.54
Site Minneapolis
Web InterfaceMonitor
XML BrokerMonitor
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• Web Interface Monitor• Type:
Citrix-Web-Interface• Secure or unsecure• Interrogates the Site Path
• If monitor does not receive valid response,considered unavaialble
Component LayerNetScaler Smart Monitors Configuration
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Component Layer
• XML Broker Monitor• Type:
Citrix-XML-Service• Secure or unsecure• Interrogates defined
published application• Checks application load
• If monitor does not receive a valid response, server offline
NetScaler Smart Monitors Configuration
Intra-Site Layer
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Intra-Site LayerOverview
Access Gateway Web Interface XML Broker
• Provides secure-remote access
• Failure results in lost connections
• Solution:
• Single point of access for applications
• Failure results in no new connections
• Solution:
• Application authentication, enumeration and launch
• Failure results in no new connections
• Solution:
24© 2008 Citrix Systems, Inc. — All rights reserved
Intra-Site Layer
• Access Gateway• Active-Passive configuration• Configurations and SSL sessions synchronized • Failure of active device results in no downtime as passive takes control immediately
• Web Interface• Balance to a group of Web Interface servers via a single IP• Verify availability before directing requests to server with smart monitor• Session persistence required
• XML Broker• Balance to a group of XML Broker servers via a single IP• Verify availability before directing requests to server with smart monitor
NetScaler High-Availability and Server Load Balancing
25© 2008 Citrix Systems, Inc. — All rights reserved
XML Broker HAVIP: 172.16.0.24
Web Interface HAVIP: 172.16.0.23
Intra-Site LayerArchitecture
Access Gateway172.16.0.22
User
Web Interface172.16.0.51
Web Interface172.16.0.52
XML Broker172.16.0.53
XML Broker172.16.0.54
Site Minneapolis
26© 2008 Citrix Systems, Inc. — All rights reserved
Intra-Site Layer
• Overview• Setup devices in HA Pair• Active-Passive operating mode• Configuration synchronized
between set• SSL sessions synchronized
between devices
• Failover• Passive Access Gateway takes
over immediately• SSL sessions remain active
NetScaler High-Availability Configuration
27© 2008 Citrix Systems, Inc. — All rights reserved
Intra-Site Layer
• Configuration• Wizard-based configuration
Load Balancing for Citrix XenApp• Virtual IP address• Web Interface port/protocol• Physical IP addresses• Smart Monitor integrated
in wizard
• Failover• New requests sent to
available server
Web Interface High-Availability Configuration
28© 2008 Citrix Systems, Inc. — All rights reserved
Intra-Site Layer
• Overview• Wizard-based configuration• Virtual IP address• XML Broker port/protocol• Physical IP addresses• Smart Monitor integrated
in wizard
• Failover• New requests sent to
available server
XML Broker High-Availability Configuration
29© 2008 Citrix Systems, Inc. — All rights reserved
Intra-Site Layer
• XML Monitor• Health Check: User an application name that does not change
• Web Interface• Persistence required, use Cookie then Session
Best Practices
Inter-Site Layer
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Inter-Site LayerOverview
Data Center
• With one URL, always receive applications
• Assess entire site availability before directing users
• Solution:
32© 2008 Citrix Systems, Inc. — All rights reserved
Inter-Site Layer
• Send users to sites with complete availability
• Focus on critical layers of XenApp architecture• Access Gateway• Web Interface• XML Broker
• Numerous configuration options• Active-Active or Active-Passive• Least response time, round robin, least connections, proximity
NetScaler Global Server Load Balancing
33© 2008 Citrix Systems, Inc. — All rights reserved
XML Broker HAVIP: 172.16.0.29
Web Interface HAVIP: 172.16.0.28
Inter-Site LayerArchitecture
Access Gateway172.16.0.22
User
Web Interface172.16.0.51
Web Interface172.16.0.52
XML Broker172.16.0.53
XML Broker172.16.0.54Site Minneapolis
Access Gateway172.16.0.26 Web Interface
172.16.0.56XML Broker172.16.0.57
Site Ft. Lauderdale
DNS
XML Broker HAVIP: 172.16.0.24
Web Interface HAVIP: 172.16.0.23
34© 2008 Citrix Systems, Inc. — All rights reserved
Intra-Site Layer
• Overview• GSLB Wizard• Set FQDN• Add local site• Configure remote site
• Failover• New requests routed to next
preferred site
NetScaler Global Server Load Balancing Configuration
35© 2008 Citrix Systems, Inc. — All rights reserved
Inter-Site Layer
• Available sites must have• Access Gateway• XML Broker• Web Interface
• Use Smart Monitors to determine site availability
Best Practices
Next Steps
37© 2008 Citrix Systems, Inc. — All rights reserved
Conclusion
• Disasters happen from minor acts too• Thunderstorms• Traffic accident• Even chipmunks
• Provide avaiability for most criticalXenApp components
• Go beyond simple monitoring of components, validate functionality
• Download Trial XenServer and NetScaler
• Obtain materials from Citrix.com–Reference Architecture (CTX117933)–Implementation Guide (CTX117934)
• Setup solution in test environment
• Build into production system
39© 2008 Citrix Systems, Inc. — All rights reserved
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