1. Clustering Servers Chapter Seven

2. Exam Objectives in this Chapter:  Plan services for high availability Plan a high availability solution that uses clustering services Plan a high availability solution that uses Network Load Balancing  Implement a cluster server Recover from cluster node failure  Manage Network Load Balancing. Tools might include the Network Load Balancing Manager and the WLBS cluster control utility

3. Lessons in this Chapter:  Understanding Clustering  Using Network Load Balancing  Designing a Server Cluster

4. Understanding Clustering  A cluster is a group of two or more servers dedicated to running a specific application (or applications) and connected to provide fault tolerance and load balancing.  Clustering is intended for organizations running applications that must be available, making any server downtime unacceptable. failover  In a server cluster, each computer is running the same critical applications, so that if one server fails, the others detect the failure and take over at a moment’s notice. This is called failover.

5. Understanding Clustering failback  When the failed node returns to service, the other nodes take notice and the cluster begins to use the recovered node again. This is called failback.  Clustering capabilities are installed automatically in the Windows Server 2003 operating system.

6. Clustering Types  Windows Server 2003 supports two different types of clustering: Server clusters and Network Load Balancing (NLB).  Important Server clustering is intended to provide high availability for applications, not data. Do not mistake server clustering for an alternative to data availability technologies, such as RAID (redundant array of independent disks) and regular system backups.

7. Server Clusters  Server clusters are designed for applications that have long-running in- memory states or large, frequently changing data sets.  These are called stateful applications, and include database servers such as Microsoft SQL Server, e-mail and messaging servers such as Microsoft Exchange, and file and print services.

8. Server Clusters  In a server cluster, all the computers (called nodes) are connected to a common data set, such as a shared SCSI bus or a storage area network.  Example of a simple two-node cluster: Server NAS

9. Server Clusters  A server cluster has its own name and Internet Protocol (IP) address, separate from those of the individual computers in the cluster.  Therefore, when a server failure occurs, there is no apparent change in functionality to the clients, which continue to send their requests to the same destination.  The passive node takes over the active role almost instantaneously, so there is no appreciable delay in performance.

10. Network Load Balancing  Network Load Balancing  Network Load Balancing (NLB) is another type of clustering that provides high availability and high reliability, with the addition of high scalability as well.  NLB is intended for applications with relatively small data sets that rarely change (or may even be readonly), and that do not have long-running in-memory states. stateless applications  These are called stateless applications, and typically include Web, File Transfer Protocol (FTP), and virtual private network (VPN) servers.

11. Network Load Balancing and Replication  Network Load Balancing is clearly not suitable for stateful applications such as database and e-mail servers.  It is possible to replicate data between the servers in an NLB cluster, for example, to prevent administrators from having to copy modified Web pages to each server individually. However, this replication is an occasional event, not an ongoing occurrence.

12. Network Load Balancing and Replication  Network Load Balancing provides scalability in addition to availability and reliability, because all you have to do when traffic increases is add more servers to the cluster.

13. Exam Tip server clusterNetwork Load Balancing cluster  Be sure you understand the differences between a server cluster and a Network Load Balancing cluster, including the hardware requirements, the difference between stateful and stateless applications, and the types of clusters supported by the various versions of Windows Server 2003.

14. Designing a Clustering Solution  Clustering can provide a solution that protects against three different types of failures: Software failures Hardware failures Site failures

15. Estimating Availability Requirements  The degree of availability you require depends on a variety of factors The nature of the applications The size Location Distribution of your user base,  The amount of availability an organization requires for its applications can affect its clustering configuration in several ways, including The type of clustering you use The number of servers in the cluster The distribution of applications across the servers in the cluster, and The locations of the servers

16. Scaling Clusters  There are two basic methods of increasing cluster performance, which are as follows: Scaling up  Adding random access memory (RAM) or level 2 (L2) cache memory, upgrading to faster processors, and installing additional processors are all ways to scale up a computer Scaling out  Adding servers to an existing cluster

17. Real World  Scalability in the Real World Note page 7-8

18. How Many Clusters?  If you want to deploy more than one application with high availability, you must decide how many clusters you want to use.

19. Two Methods of Clustering Apps  A cluster with two applications  Two separate clusters running two different applications App 1 App 2 App 1 App 2

20. Combining Clustering Technologies  Two active notes sharing a single passive node  NLB Cluster interacting with a server cluster App 1 App 1 App 2 App 2 NLB Cluster Server Cluster

21. Dispersing Clusters  Deploying geographically dispersed clusters enables applications to remain available in the event of a catastrophe that destroys a building or even a city.  Having cluster servers at different sites can also enable users to access applications locally, rather than having to communicate with a distant server over a relatively slow wide area network (WAN) connection.

22. Using Network Load Balancing  Understanding Network Load Balancing 32 servers A Network Load Balancing cluster consists of up to 32 servers, referred to as hosts, each of which is running a duplicate copy of the application you want the cluster to provide to clients. virtual network adapter Network Load Balancing works by creating on each host a virtual network adapter that represents the cluster as a single entity.

23. Planning a Network Load Balancing Deployment  NLB Network Design Internet Internet router Firewall Switch Node

24. NLB Operational Modes  The servers that are going to be the hosts in your NLB cluster do not require any special hardware. Installing a second network interface adapter  Two operational modes:  unicast mode and  multicast mode.  In unicast mode, Network Load Balancing replaces the MAC address of the physical network interface adapter in each server with the MAC address of the virtual adapter representing the cluster.  The Address Resolution Protocol (ARP) resolves both of the server’s IP addresses (the IP address originally assigned to the network interface adapter and the cluster IP address) to the single MAC address for the cluster.

25. NLB and ARP  ARP is a TCP/IP protocol that resolves IP addresses into MAC or hardware addresses.  To transmit to a particular IP address, a TCP/IP computer must first discover the MAC address associated with that IP address, so that it can build a datalink layer protocol frame.  ARP functions by transmitting a broadcast message containing an IP address to the local network.  ARP requests that contain either its original IP address or the cluster IP address by sending a response containing the cluster MAC address.  Therefore, no computer on the network can transmit to the MAC address assigned for NLB server’s physical network interface adapter.

26. NLB and ARP  Because the network interface adapters of all the servers in the cluster have the same MAC address, the cluster servers cannot communicate among themselves in the normal way, using their individual MAC addresses.  Note table 7-1 on page 18

27. NLB Networking  Important A single computer running Windows Server 2003 cannot be a member of a Network Load Balancing cluster and a server cluster at the same time, because these two clustering solutions use network interface adapters in different ways. If you want to deploy both an NLB cluster and a server cluster on your network, you must use separate servers for each cluster.

28. NLB Networking  Note Because all the servers in the cluster are using the same cluster MAC address, transmitting the heartbeats is simply a matter of directing the packets to that address. The servers don’t need to broadcast the heartbeat messages, reducing the impact of the cluster traffic on the network.

29. Deploying a Network Load Balancing Cluster  The basic steps in deploying NLB for a cluster of Web servers on a perimeter network are found on page 7-20.

30. Monitoring Network Load Balancing  Using Network Load Balancing Manager

31. Monitoring Network Load Balancing  Using Event Viewer

32. Using Nlb.exe  A command line using a utility Some of the program’s most useful parameters are as follows:  display  drain port  drainstop  params  Example print out on pages 23 – 24.  query  queryport port

33. Exam Tip NLB.EXE WLBS.EXE  Be sure to understand that the NLB.EXE and WLBS.EXE programs are one and the same, with identical functions and parameters

34. Practice:  Creating a Network Load Balancing Cluster Exercise 1: Installing IIS  Page 7-25 Exercise 2: Creating a Network Load Balancing Cluster  Page 7-26 Exercise 3: Testing the Cluster  Page 7-28

35. Designing a Server Cluster  Designing a Server Cluster Deployment

36. Planning a Server Cluster Hardware Configuration  Using SCSI  Understanding SCSI  Using Fibre Channel  Fibre Channel Arbitrated Loop  Fibre Channel Switched Fabric

37. Using SCSI Server Storage  Cluster using a SCSI bus

38. Fibre Channel Arbitrated Loop Server Storage  Cluster using a Fibre Channel arbitrated Loop

39. Fibre Channel Switched Fabric Storage Server Fibre Channel Switch  Cluster using a Fibre Channel switched fabric

40. Creating an Application Deployment Plan  Windows Server 2003 can host the following two basic types of applications in a server cluster: Single-instance applications Multiple-instance applications

41. Deploying Multiple-Instance Applications  Partitioning an application means that you split the application’s functionality into separate instances and deploy each one on a separate cluster node. Database A to GH to LM to ST to Z Server

42. Selecting a Quorum Model  Server clusters running Windows Server 2003 support the following three types of quorum models: Definitions on page 7-38 Single-node cluster Single-quorum device cluster Majority node set cluster

43. Exam Tip  Be sure to understand the differences between the various quorum models supported by Windows Server 2003.

44. Creating a Server Cluster  To create a new cluster, you must have the following information available: The name of the domain in which the cluster will be located The host name to assign to the cluster The static IP address to assign to the cluster The name and password for a cluster service account

45. Creating a Server Cluster  Some of the configuration tasks you can perform in Cluster Administrator are as follows: Create resource groups Define resource dependencies Configure the cluster network role Configure failover relationships

46. Exam Tip  It is a good idea to spend some time exploring the Network Load Balancing Manager and Cluster Administrator applications. Learn the function of each parameter or setting in these two programs, using the online help for assistance.

47. Configuring Failover Policies  Some of the failover policies you might consider using are as follows: Failover pairs Hot-standby server N+I Failover ring Random

48. Practice:  Creating a Single Node Cluster Exercise 1: Creating a Server Cluster  Page 7-42 Exercise 2: Creating a Cluster Resource  Page 7-43 Exercise 3: Access the Server Cluster  Page 7-44

49. Summary  Case Scenario Exercise Page 7-46  Troubleshooting Lab Page 7-48  Exam Highlights Page 7-49 Key Points Key Terms