1. 70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network, Enhanced Chapter 12: Planning and Implementing Server Availability and Scalability

2. Objectives Understand availability and scalability
Differentiate between server clustering and Network Load Balancing
Implement server clustering
Describe the concepts involved in server clustering
Describe the concepts involved in Network Load Balancing
Implement Network Load Balancing
Install applications on an NLB cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

3. Availability and Scalability
Availability: the percentage of time that servers are providing service on the network
Scalability: the ability to expand the number of clients or data that a server can support
How you implement availability and scalability depends on whether applications are stateful or stateless
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

4. Server Availability Potential causes of server or service failure
Hardware failure
Network failure
Administrator mistakes
Operating system crashes
Application crashes
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

5. Server Availability (continued)
To provide higher server availability, you can use:
Redundant hardware (e.g., RAID5)
Uninterruptible power supply for temporary power outages
Backup power generator for longer power outages
Redundant paths through the network
Standardized procedures to perform tasks
Fully document the network server configuration
Regularly patched operating systems and applications
Windows Server 2003 clustering to implement server clusters and Network Load Balancing
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

6. Scalability Scalability can be accomplished by: To scale up, you can:
Scaling up
Scaling out
To scale up, you can:
Add more RAM
Add a faster disk subsystem
Add more processors
Scaling up can be both limiting and expensive
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

7. Scalability (continued)
Scaling out uses commonly available hardware rather than specialized hardware
Difficult when a single service is running on a server and you want to scale out
Network Load Balancing (NLB)
Best solution for scaling out a single application
Can distribute the load between multiple servers
NLB can sense a failed server
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

8. Stateful and Stateless Applications
Stateful applications require the server to retain knowledge about the client accessing the server
Not well suited to scale out
Easier to scale up
Stateless applications do not require the server to retain knowledge about the client accessing the server
Well suited to scale out
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

9. Windows Server 2003 Clustering
Windows Server 2003 provides two clustering mechanisms to provide availability and scalability:
Server clusters
NLB
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

10. Server Clusters Provides highly available services
A service runs on a single server and can be moved to another server in the cluster (failover)
Server clusters are available only in Windows Server 2003, Enterprise Edition and Datacenter Edition
Up to eight nodes are supported in each server cluster
Server clusters must have a shared storage
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

11. Server Cluster Configurations
Windows Server 2003 supports:
Active/Passive
Consists of two nodes: one hosts services and the other does not
N+I failover
N nodes in the server cluster are active and I nodes are passive in the server cluster ready to accept failed over services
Active/Active
Consists of two or more nodes, all of which are active
Single node virtual server
Consists of only one node. and does not have failover capability
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

12. Cluster Applications To use server clusters, application must be
An IP-based protocol
Able to specify where application data is located
Able to use the clustering API and receive status notifications and manage the cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

13. Network Load Balancing
Network Load Balancing (NLB) spreads application requests from clients among two or more servers
With NLB, an application is installed on multiple servers using a virtual IP address
NLB can spread network requests evenly among the servers hosting the application or spread network requests based on a weighting scheme
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

14. An Example of Windows Server 2003 Clustering
The following example illustrates how both server clusters and NLB can be used for a Web-based application designed to explore a computerized web based database backed school registration system
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

15. An Example of Windows Server 2003 Clustering (continued)
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

16. Activity 12-1: Cluster Concepts
The purpose of this activity is to learn more about server clusters and NLB
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

17. Installing and Configuring Server Clusters
The cluster service is installed automatically as part of a Windows Server 2003 installation
To configure a server cluster, you use Cluster Administrator
To create new server clusters or
Add new nodes to an existing server cluster
New Server Cluster Wizard: creates a new cluster
After installation, the current state of your cluster is shown in Cluster Administrator
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

18. Activity 12-2: Installing a Single Node Virtual Server Cluster
The purpose of this activity is to create a single node virtual server cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

19. Server Cluster Concepts
The various concepts about server clusters include:
Shared disks
Quorum resource
Cluster communication
Resource groups
Failover and failback
Virtual servers
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

20. Shared Disks
Shared disk: storage that all nodes in a cluster can access
Not required when a geographically dispersed server cluster is configured with an alternate data synchronization mechanism, or when a server cluster has a single server for testing purposes
When shared disks are required use either
A shared SCSI bus or
Fibre Channel SAN
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

21. Shared SCSI Bus SCSI configuration requirements include
An SCSI card that can disable autobus reset
All SCSI devices on the SCSI must have unique SCSI IDs
Proper termination on the SCSI bus
SCSI hard drives that are multi-initiator enabled to support multiple SCSI cards on the bus
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

22. Shared SCSI Bus (continued)
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

23. Fibre Channel Fibre Channel is for storage area networks
Requirements for Fibre Channel shared storage
Fibre Channel card for each node in the server cluster
External storage array that supports Fibre Channel
Fibre Channel switch to connect the nodes to the external storage array
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

24. Fibre Channel (continued)
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

25. Quorum Resource Quorum Resource is used by the cluster service
To store configuration information
To arbitrate which node owns the cluster
The location is specified at server cluster creation
Only one node at a time can own the quorum resource
First available node becomes the owner
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

26. Cluster Communication
Nodes in a server cluster communicate with each other using heartbeat packets
Heartbeat packets monitor which nodes in the server cluster are still up and available
Can be UDP unicast packets or multicast packets
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

27. Resource Groups
Control of services and applications in a server cluster is based on resource groups
Resource group: logical grouping of all required resources for an application or service to run
Resources can be disk partitions, IP addresses, printers, services, and applications
Resources can be in the following states: online, offline, online pending, offline pending or failed
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

28. Failover and Failback
If a server cluster node fails, the resource groups on that node automatically fail over to another node
After failover has occurred, failback is possible
Occurs when the original node hosting a resource group is available again and the resource group is moved back to the original node
Can define whether a resource group fails back automatically, manually, or not at all
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

29. Virtual Servers
Virtual server: collection of resources in a resource group presented by the cluster service
The node that owns the group responds on its behalf
Resources in server clusters are always accessed through a virtual server
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

30. Activity 12-3: Adding a Printer to a Virtual Server
The purpose of this activity is to add a printer to a virtual server
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

31. Activity 12-4: Removing a Server Cluster Node
The purpose of this activity is to remove the final node from a server cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

32. Network Load Balancing Concepts
Concepts in NLB include:
The NLB driver
Virtual IP addresses
Application requirements
Affinity
Load balancing options
Network communication
Port rules
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

33. NLB Driver
NLB driver: software responsible for performing NLB on each host in an NLB cluster
Operates between the network card driver and the IP protocol
Can intercept and filter all incoming IP traffic
Filtering is required because all hosts in an NLB cluster share a MAC address that is used for the cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

34. Activity 12-5: Enabling the NLB Driver
The purpose of this activity is to enable the NLB driver
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

35. Virtual IP Address Each NLB cluster has a virtual IP address
The virtual IP address must be
Unique on the network
On the same subnet as the hosts in the NLB cluster
Added as a secondary IP address to a network interface
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

36. Application Requirements
NLB suitable applications must:
Must use TCP or UDP
Data modified by the clients must be synchronized between hosts in the NLB cluster or stored in a central location, or affinity must be configured
Session state information must be stored on client computers or central location, or affinity must be configured
The application must not bind to a computer name
Applications must not keep files open for writing
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

37. Affinity
Affinity: responses to requests made originally to one host in an NLB cluster are directed back to the original host
Required for applications that track session state info
Affinity can be configured in three ways:
None: affinity is not performed for stateless applications
Single: affinity based on the source IP address of the client
Class C: affinity is based on the source network of the client.
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

38. Load Balancing Options
When hosts are part of an NLB cluster, you can define how the load is balanced between them:
Multiple Host and Equal
NLB cluster distributes load evenly between all hosts in cluster
Multiple Host and Load weight
NLB cluster distributes requests based on a load weight
Single Host
All requests to the NLB cluster are directed to a single host
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

39. Network Communication
All hosts in the NLB cluster share a MAC address
All client requests use the MAC address of the NLB cluster as the destination MAC address
Allows all hosts in the NLB cluster to receive packets addressed to the NLB cluster
NLB driver loaded on each host accepts or discards the packet based on an algorithm that takes into account affinity settings, load weighting, and priority
NLB clusters can be configured to use either unicast MAC addresses or multicast MAC addresses
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

40. Unicast
Unicast is the most common method used for distributing client requests
When selected, all hosts in the NLB cluster use the same unicast MAC address
Unicast MAC address is used in place of the MAC address embedded in the network card of each host
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

41. Multicast
Multicast MAC addresses: prevent the inefficient use of switches and allow NLB cluster hosts with a single network to communicate among themselves
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

42. Port Rules Port rules Control what the NLB driver does with packets
When hosts in the NLB cluster receive packets from clients, port rules define what is done with each packet
Composed of
Cluster IP address
Port address range
Protocol
Filtering mode that includes load weight and affinity
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

43. Implementing Network Load Balancing
To implement an NLB cluster
NLB driver must be enabled on all servers that are to be hosts in the NLB cluster
Can create a new NLB cluster using Network Load Balancing Manager (nlbmgr.exe)
After the first host has created the NLB cluster, others can join
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

44. Activity 12-6: Installing an NLB Cluster
The purpose of this activity is to install an NLB cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

45. Installing Applications on an NLB Cluster
No special procedure to use when installing applications on an NLB cluster
Application must be installed on all hosts in cluster
Microsoft recommends that you automate the process of application configuration to ensure that all servers are configured exactly the same
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

46. Activity 12-7: Configuring a Web Application for Load Balancing
The purpose of this activity is to configure a Web site for load balancing
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

47. Activity 12-8: Removing an NLB Clustered Application
The purpose of this activity is to remove an NLB cluster
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

48. Summary
Availability: percentage of time that servers are providing service on the network
Scalability: ability to expand the number of clients or data that a server can support
Windows Server 2003 provides two clustering mechanisms to provide availability and scalability: server clusters and NLB
In a server cluster a service runs on a single server and can be moved to another server (failover)
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network

49. Summary (continued)
Network Load Balancing (NLB) spreads application requests from clients among two or more servers
NLB Manager is used to implement NLB
When implementing NLB, Microsoft recommends that you automate the process of application configuration to ensure that all servers are configured exactly the same
70-293: MCSE Guide to Planning a Microsoft Windows Server 2003 Network