high-availability for xenapp with xenserver and...

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


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


Disaster Recovery

Layered High-Availability


High-Availability Layers

• Hardware

• Components• XML Broker• Web Interface• Mission critical XenApp Servers

• Intra-Site

• Inter-Site


Initial Architecture

Access Gateway172.16.0.22


User

User Web Interface172.16.0.51

Web Interface172.16.0.52

XML Broker172.16.0.53




Site Minneapolis

Site Ft. Lauderdale

Hardware Layer


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


Shared Storage

Hardware LayerXenMotion


• 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


High Availability

Shared Storage


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


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


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


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

http://www.company.com/Citrix/AccessPlatform/site/default.aspx


Component LayerArchitecture






Site Minneapolis

Web InterfaceMonitor

XML BrokerMonitor


• 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


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


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:


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


XML Broker HAVIP: 172.16.0.24

Web Interface HAVIP: 172.16.0.23

Intra-Site LayerArchitecture


User





Site Minneapolis


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


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


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


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


Inter-Site LayerOverview

Data Center

• With one URL, always receive applications

• Assess entire site availability before directing users

• Solution:


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




Inter-Site LayerArchitecture


User




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




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


Inter-Site Layer

• Available sites must have• Access Gateway• XML Broker• Web Interface

• Use Smart Monitors to determine site availability

Best Practices

Next Steps


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


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