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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
4© 2007 Citrix Systems, Inc. — All rights reserved
Determine If There Is A Need
•Break it down into small components• Server Load Balancing• Global Server Load Balancing
5© 2007 Citrix Systems, Inc. — All rights reserved
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
6© 2007 Citrix Systems, Inc. — All rights reserved
Server Load Balancing - Qualification
•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
7© 2007 Citrix Systems, Inc. — All rights reserved
Server Load Balancing - Qualification
•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
8© 2007 Citrix Systems, Inc. — All rights reserved
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
9© 2007 Citrix Systems, Inc. — All rights reserved
Global Server Load Balancing - Qualification
•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
10© 2007 Citrix Systems, Inc. — All rights reserved
Global Server Load Balancing - Qualification
•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
11© 2007 Citrix Systems, Inc. — All rights reserved
AVAILABLE TOOLS: REFERENCE ARCHITECTURE
Terminology
13© 2007 Citrix Systems, Inc. — All rights reserved
Basic Citrix NetScaler LB Concept
Service
Monitor
Service
Monitor
Server
Server
vserver
14© 2007 Citrix Systems, Inc. — All rights reserved
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
15© 2007 Citrix Systems, Inc. — All rights reserved
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
16© 2007 Citrix Systems, Inc. — All rights reserved
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
17© 2007 Citrix Systems, Inc. — All rights reserved
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
18© 2007 Citrix Systems, Inc. — All rights reserved
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
19© 2007 Citrix Systems, Inc. — All rights reserved
High Availability• Deployed in HA for maximum uptime
• Diagrams• Only show 1 NetScaler for readability• Assumption is deployment of HA pairs
• Remember
=
20© 2007 Citrix Systems, Inc. — All rights reserved
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
22© 2007 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 Interface172.16.0.56
XML Broker172.16.0.57
Site MSP
Site FLL
23© 2007 Citrix Systems, Inc. — All rights reserved
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
24© 2007 Citrix Systems, Inc. — All rights reserved
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
26© 2007 Citrix Systems, Inc. — All rights reserved
Web Interface and XML Broker Load BalancingBefore
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
27© 2007 Citrix Systems, Inc. — All rights reserved
Web Interface and XML Broker Load BalancingAfter
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
WI VIP:172.16.0.22
XML VIP:172.16.0.23
28© 2007 Citrix Systems, Inc. — All rights reserved
• Prepare the NetScalers
• Server Load Balancing Configuration
StepsWeb Interface and XML Broker Load Balancing
29© 2007 Citrix Systems, Inc. — All rights reserved
Server Load Balancing Summary
NetScaler172.16.0.21
Web Interface172.16.0.51
XML Broker172.16.0.53
XML Broker172.16.0.54
Web Interface172.16.0.52
MonitorCTXWEBSite Path
MonitorCTXXMLNotepad
MonitorCTXWEBSite Path
MonitorCTXXMLNotepad
SLB Service172.16.0.53
HTTP 80
SLB Service172.16.0.52
HTTP 80
SLB vserver172.16.0.24
SLB Service172.16.0.54
HTTP 80
SLB Service172.16.0.51
HTTP 80
SLB vserver172.16.0.23
Phase II: Farm Reconfiguration
31© 2007 Citrix Systems, Inc. — All rights reserved
Farm ReconfigurationBefore
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
WI VIP:172.16.0.22
XML VIP:172.16.0.23
32© 2007 Citrix Systems, Inc. — All rights reserved
Farm ReconfigurationAfter
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
WI VIP:172.16.0.22
XML VIP:172.16.0.23
33© 2007 Citrix Systems, Inc. — All rights reserved
• Reconfigure Web Interface
• Reconfigure Access Gateway
• Test
StepsFarm Reconfiguration
34© 2007 Citrix Systems, Inc. — All rights reserved
STA Load Balancing• Do not change the Access Gateway STA settings• Correct STA selected based on STA identifier• Load balancing breaks this functionality
35© 2007 Citrix Systems, Inc. — All rights reserved
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
37© 2007 Citrix Systems, Inc. — All rights reserved
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
38© 2007 Citrix Systems, Inc. — All rights reserved
Global Server Load Balancing Preview
Web Interface172.16.0.51
XML Broker172.16.0.53
XML Broker172.16.0.54
Web Interface172.16.0.52
MonitorCTXWEBSite Path
MonitorCTXXMLNotepad
MonitorCTXWEBSite Path
MonitorCTXXMLNotepad
SLB Service172.16.0.53
HTTP 80
SLB Service172.16.0.52
HTTP 80
SLB vserver172.16.0.24
SLB Service172.16.0.54
HTTP 80
SLB Service172.16.0.51
HTTP 80
SLB vserver172.16.0.23
Access Gateway172.16.0.22
GSLB Monitor
SSL
GSLB MonitorHTTP
GSLB MonitorHTTP
GSLB Service172.16.0.22
SSL 443
GSLB vserverSSL 443
agee.company.com
39© 2007 Citrix Systems, Inc. — All rights reserved
• Build GSLB Sites
• Build GSLB Monitors
• Build GSLB Services
• Build GSLB Virtual Server
• Update DNS
• Test
StepsGlobal Server Load Balancing Configuration
40© 2007 Citrix Systems, Inc. — All rights reserved
Global Server Load Balancing Summary
Web Interface172.16.0.51
XML Broker172.16.0.53
XML Broker172.16.0.54
Web Interface172.16.0.52
MonitorCTXWEBSite Path
MonitorCTXXMLNotepad
MonitorCTXWEBSite Path
MonitorCTXXMLNotepad
SLB Service172.16.0.53
HTTP 80
SLB Service172.16.0.52
HTTP 80
SLB vserver172.16.0.24
SLB Service172.16.0.54
HTTP 80
SLB Service172.16.0.51
HTTP 80
SLB vserver172.16.0.23
Access Gateway172.16.0.22
GSLB Monitor
SSL
GSLB MonitorHTTP
GSLB MonitorHTTP
GSLB Service172.16.0.22
SSL 443
GSLB vserverSSL 443
agee.company.com
41© 2007 Citrix Systems, Inc. — All rights reserved
Final Architecture
NetScaler172.16.0.21
NetScaler172.16.0.26
Web Interface172.16.0.51
Web Interface172.16.0.52
XML Broker172.16.0.54
Web Interface172.16.0.56
XML Broker172.16.0.57
Site MSP
Site FLLUser
DNS
WI VIP:172.16.0.22
XML VIP:172.16.0.23
XML Broker172.16.0.53
WI VIP:172.16.0.22
XML VIP:172.16.0.23
42© 2007 Citrix Systems, Inc. — All rights reserved
AVAILABLE TOOLS: IMPLEMENTATION GUIDE
Summary
44© 2007 Citrix Systems, Inc. — All rights reserved
• 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
45© 2007 Citrix Systems, Inc. — All rights reserved
• 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
46© 2007 Citrix Systems, Inc. — All rights reserved