nikolay sh gslb for xen app

High Availability for XenApp

Nikolay ShadrinSystems Engineer

2© 2007 Citrix Systems, Inc. — All rights reserved

Agenda

Agenda item number 1

Education

Implementation

Conclusion

Identification

Where It Fits


Determine If There Is A Need

•Break it down into small components• Server Load Balancing• Global Server Load Balancing


Server Load Balancing - Qualification

•Does the architecture have multiple • Access Gateway devices• Web Interface servers• XML Brokers

•No: Single Point of Failure•Yes: How are they load balanced



•How are they load balanced• DNS Round Robin• Hardware or Software Load Balancer

•DNS: Not an intelligent solution•Hardware or Software:

How does it determine availability

DNS



•Hardware or Software: How does it determine availability• Server availability: A service could still be offline and the load balancer would

not detect• Service availability: Identify if the service is online, but could still be non-

functioning• Service response: Intelligent solution as verifies services are running and

responding correctly

•NetScaler provides service response analysis with• Web Interface monitor• XML Broker monitor


Global Server Load Balancing - Qualification

• Is the environment spread across multiple sites?• No: No need for GSLB but there is a

site failure risk• Yes



•How are the sites load balanced?• Multiple Addresses: Not intelligent and requires users to remember different

access scenarios• DNS Round Robin: Not intelligent• Hardware Load Balancer Solution



•How is the harware load balancer monitoring site availability?• Server Response: Server could respond, but services not available• Service Availability: Service could be running but not functioning• Service Response: Verifies services are responding correctly.

•NetScaler uses service response for XenApp•NetScaler combines multiple services to determine site

availability


AVAILABLE TOOLS: REFERENCE ARCHITECTURE

Terminology


Basic Citrix NetScaler LB Concept

Service

Monitor

Service

Monitor

Server

Server

vserver


Service

Monitor

Service

Monitor

Server

Server

vservervserver

Service

Monitor

Service

Monitor

Server

Server

vservervserver

What is a vserver?

• Object on NetScaler that receives client connections/requests

• Distributes client requests among bound services

• Can be used for external and internal-only resources


Service

Monitor

Service

Monitor

Server

Server

vserver

Service

Service

Service

Monitor

Service

Monitor

Server

Server

vservervserver

What is a Service?

Service

Service

• Network endpoint• Server IP• Server Port• Protocol

• Services bound to a vserver

• Service can represent • A server running Web Interface• A server running as a XML Broker


Service

Monitor

Service

Monitor

Server

Server

vserver

Monitor

Monitor

Service

Monitor

Service

Monitor

Server

Server

vserver

What is a Monitor?

Service

Service

Monitor

Monitor

• Periodic probe of a server or service

• Monitors are bound to services

• Verifies health of the bound service

• Provides feedback to NetScaler kernel


Load Balancing Method

• Used to determine appropriate backend system to forward requests to• Least Connections (default)• Round Robin• Least Response Time• Least Bandwidth• Least Packets• Token• Hashing (of URL, Domain name, Source/Destination IP Address)• Round Trip Time (RTT)• Source/Destination IP Hash

Service

Monitor

Service

Monitor

Server

Server

vserver

Monitor

Monitor

Service

Monitor

Service

Monitor

Server

Server

vserver


Service

Monitor

Service

Monitor

Server

Server

vserver

Persistence methods

• Used to keep clients going to the same server/service

• Typical persistance methods:• Source-IP• Cookie Insert• SSL Session ID• URL Passive• Custom Server ID• Rule

Service

Monitor

Service

Monitor

Server

Server

vserver


High Availability• Deployed in HA for maximum uptime

• Diagrams• Only show 1 NetScaler for readability• Assumption is deployment of HA pairs

• Remember

=


Terminology Summary

Terminology Definition

vserver Virtual IP address on the NetScaler switch for the load balanced pool

Server Interface IP of a physical server included in a load balanced group

Service The port and protocol being load balanced on a server

Monitor The method used to assess server availability and response time

Load balancing method The method by which traffic is distributed among the services

Persistence The method used for maintaining client-server affinity

Proof of ConceptWalk Through


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 MSP

Site FLL


Initial Architecture Challenges

• Possibility of users being denied their applications• Web Interface: Not load balanced, manual change if primary fails• Access Gateway Web Interface Site: Can only configure a single Web Interface• XML Black Hole: Service is available but not functioning• Site B Failure: Multiple single points of failure

• Configuration challenges• Similar devices have different configurations


Initial Architecture Solution

• Upgrade to NetScaler-Enterprise or Platinum from• Secure Gateway• Access Gateway (All Editions)

• NetScaler-Enterprise or Platinum gets you• Server Load Balancing• Global Server Load Balancing• Access Gateway Enterprise SSL-VPN

• Three phased approach:• Phase I: Server Load Balancing• Phase II: Farm Reconfiguration• Phase III: Global Server Load Balancing

Phase I: Server Load Balancing


Web Interface and XML Broker Load BalancingBefore







Web Interface and XML Broker Load BalancingAfter






WI VIP:172.16.0.22

XML VIP:172.16.0.23


• Prepare the NetScalers

• Server Load Balancing Configuration

StepsWeb Interface and XML Broker Load Balancing


Server Load Balancing Summary

NetScaler172.16.0.21





MonitorCTXWEBSite Path

MonitorCTXXMLNotepad



SLB Service172.16.0.53

HTTP 80


HTTP 80

SLB vserver172.16.0.24


HTTP 80


HTTP 80


Phase II: Farm Reconfiguration


Farm ReconfigurationBefore






WI VIP:172.16.0.22

XML VIP:172.16.0.23


Farm ReconfigurationAfter






WI VIP:172.16.0.22

XML VIP:172.16.0.23


• Reconfigure Web Interface

• Reconfigure Access Gateway

• Test

StepsFarm Reconfiguration


STA Load Balancing• Do not change the Access Gateway STA settings• Correct STA selected based on STA identifier• Load balancing breaks this functionality


Farm Reconfiguration - SummaryDevice Parameter Old Setting New SettingAG WI Home

Page172.16.0.51 172.16.0.23

WI1 & WI2

STA

XML Broker

http://172.16.0.53/pathhttp://172.16.0.54/path172.16.0.53172.16.0.54

http://172.16.0.24/path

172.16.0.24

Phase III: Global Server Load Balancing


Intelligent GSLB

• Only send users to sites with complete availability• If Access Gateway responds, the site could still

be down• Web Interface disruptions• XML Broker disruptions• STA disruptions

• Define and configure GSLB based on layers


Global Server Load Balancing Preview










HTTP 80


HTTP 80



HTTP 80


HTTP 80



GSLB Monitor

SSL

GSLB MonitorHTTP

GSLB MonitorHTTP

GSLB Service172.16.0.22

SSL 443

GSLB vserverSSL 443

agee.company.com


• Build GSLB Sites

• Build GSLB Monitors

• Build GSLB Services

• Build GSLB Virtual Server

• Update DNS

• Test

StepsGlobal Server Load Balancing Configuration


Global Server Load Balancing Summary










HTTP 80


HTTP 80



HTTP 80


HTTP 80



GSLB Monitor

SSL

GSLB MonitorHTTP

GSLB MonitorHTTP

GSLB Service172.16.0.22

SSL 443

GSLB vserverSSL 443

agee.company.com


Final Architecture








Site MSP

Site FLLUser

DNS

WI VIP:172.16.0.22

XML VIP:172.16.0.23


WI VIP:172.16.0.22

XML VIP:172.16.0.23


AVAILABLE TOOLS: IMPLEMENTATION GUIDE

Summary


• XenApp used to deliver critical line-of-business applications

• Integrate global server load balancing and server load balancing for maximum availabilty

• NetScaler integration with XenApp makes it extremely easy• XenApp load balancing wizard• Specialized monitors for Web Interface and XML Broker

Global Availability


• GSLB for XenApp: http://support.citrix.com/ • Reference Architecture• Design Considerations• Implementation Guide

• TechTalk Webcasts: http://www.citrix.com/English/NE/events/byType.asp?etype=1441

Available Tools

http://support.citrix.com/

http://www.citrix.com/English/NE/events/byType.asp?etype=1441

nikolay sh gslb for xen app

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